How To Brake?

[FTS]

Here are two schools of thought exemplified by two different "experts" (IMHO) on the topic (excerpts taken from Racer University (http://raceruniversity.com/campus/)):

Neil Roberts writes:

"Everyone will tell you that smooth is fast, but there is one exception. The power-to-braking transition at the beginning of a straight-line braking zone can and should be as abrupt as you can manage. That is how to make a pass stick and it is worth a little bit of lap time, so you want to slam the brakes on at the beginning of every straight braking zone. Of course the brakes had better be warmed up first."

Peter Krause writes:

"Jim Myers, my coach, forced me to move away from being seduced by the sensation of doing something special by "slamming" on the brakes. He refocused my attention towards "squeezing" ON the brakes earlier and, more importantly, focused me on where and how soon I could get OFF the brakes. This reduced my natural tendency to over-brake for the corner and allowed me to become comfortable introducing the slight instability required in order to begin the rotation of the car. This leads to the next phase, how to integrate the end of braking into helping the car to begin turning into the corner."

And Neil Roberts closes his views with:

"Most cars can decelerate harder than they can corner or accelerate. That’s why it takes highly developed skills to avoid braking more than you absolutely have to. As your skills and brake system tuning improve, you will find that you use the brakes harder, but for less time and distance in each braking zone. Mastering the art of deceleration is tough to do, but it is highly satisfying, and it adds to your on-track safety by enhancing your contact avoidance skills."

With all due to respect to Mr. Roberts, I am in Peter's camp on squeezing the brakes, especially during the initial application and modulating them through the whole braking zone and trailing as best as I can.


What say you all? Which technique, in general, do you subscribe to?

[TRAKCAR]

Slamming;

- Hitting the brake with your foot flying through the air on the way down?
- Getting on the brake pedal hard straight into ABS, but no air involved?

Braking is an art, certainly no expert opinion here, but I would think slamming staight into ABS (Without air) can only work in the beginning of a brake zone that is straight and gives you some time for the car to settle as you are starting to trail brake.

Or maybe where a quick stab is needed to scrub of some speed in a straight line...

I'm with Peter Krause, my laptime is mostly about how early I can get off the brake smoothly and on throttle smootly and quickly... If I can plop down the throttle I know I lost the lap.

[bman]

They taught Neil's approach at the Porsche driving school. But I've had more success with Peter's approach. Acutally somewhere in between......

Simple goal for me is to figure out how much speed I can carry into a corner. So on a corner that I am not familar with or struggling, I will brake earlier and lighter feeling my way into the corner. After I've got a sense of the momentun I can carry in, I will work on moving up the intial brake application.

[Dell]

I'd agree more with Neil's approach. I think the problem is the semantics of "slamming" the brakes. Peter's approach does have merit. But the merit is learning where to find the limit is. It is NOT the faster approach. Brake like that and you are going to get passed in every brake zone by the competition.

My approach is to brake as deep as possible and then "slam" on the brakes. The semantics of slamming should be.....get to threshold as quickly as possible.

As has been said, braking is an art and very hard to master. Some people just have a very good feel of the physics of weight transfer, brake threshold, etc..

I have NEVER got into ABS in my car. By understanding what creates the ABS situation you can understand how to take it to the razor thin edge and stay there.

Back to my style. When I slam to threshold I immediately start modulating the brake pressure to keep the stopping right at the threshold (ABS) limit. If you are not at the limit you are not maximizing your brakes and thus not grabbing all those tenths laying around the track. Your goal should be to transition from brake to throttle just after corner entry. This method allows you to maximize front end grip and to TB into the corner which results in the need for LESS steering angle and allows you to get on the throttle sooner. Again, picking up tenths all over the place. I heard a quote from Jackie Stewart once. He said that the brake and throttle were ON/OFF switches working as a single switch. You are either on brake or throttle. Coasting is the enemy of lap times and weight transfer. If there is a time gap between brake and throttle or throttle and brake you are carrying too much speed into the corner or coasting. Not good.

If you ever get to watch an F1 practice live (TV is ok but not nearly as info packed) set yourself up at a high speed straight to tight corner transition. You will think that they all forgot how to drive. Why? They are sliding off the track left and right. Their is a method to their madness. They are trying to find both the perfect brake point for transition to corner entry as well as just how much they can bite off past that perfect spot should they need to "make a move".

The problem I see is most DE guys spend the entire session trying to set personal best times instead of setting sector or turn best times. I set out a goal for a specific sector or turn and work on it at the expense of total lap time. Then data analysis tells me what works and what doesn't. Once you truly understand what works ALL THE WAY AROUND THE TRACK then you can start putting it all together.

This doesn't mean you have to work on a section all the time. Some of the best sessions are had by just running with your buddies!

[FTS]

Dell do you by any chance have data that shows the time frame between coming off throttle and max LongG readings. I'd love to be able to quantify what "slamming the brakes" is.

[TRAKCAR]

+1, I'm taking notes here!

[Dell]

Let me see what I have and post back.

[csmarx]

I'm with Peter Krause. From memory it was Sir Stirling Moss who said that the hardest thing he had to learn in racing was how to take his foot of the brake. Focusing on that certainly helped me improve lap times when I was stuck in a rut. But with the caveat that once you figure out how to take the foot off, then you can start focusing on how to engage the brake - i.e. later and harder.

Early on I used to focus more on the foot-on part, but to the detriment of my corner entry and speed. Through data analysis I finally figured out that's were I was loosing speed vs. my co-drivers.

I haven't driven much for the last 5 years, so now I'm back to developing my sensitivity to the foot-off transition.

-Christian

[FTS]

I have to admit, my weakest point is how and when I come off the brakes, for the past 6 years I have been improving, but that is still the one biggest issue I have.

[Gator Bite]

Here's another opinion, from Vic Elfords 'Porsche High Performance Driving Handbook' (http://www.amazon.com/Porsche-High-Performance-Driving-Handbook-Elford/dp/0760327548/ref=sr_1_1?ie=UTF8&s=books&qid=1305374617&sr=8-1):
"In the last chapter we saw how important smoothness is in accelerating. If anything, smoothness is even more important when it comes to braking at the limit......."

Then later,

"Although I have emphasized the importance of smoothness, here is one time when you need an abrupt little stab or jab. When your foot goes to the brake pedal the first moment should be just that - a little jab at about 4 on the scale above.

That little jab will take up the pressure in the braking system and cause an instant weight transfer toward the front wheels. As soon as that's done you can start squeezing on the pedal in earnest."

[landjet]

I've only been doing DE's for 4 years so I'm no expert. I do know that when I began I would slam on my brakes and brake more than I had to. One of my instructors worked with me on braking and got me to squeeze on the brake pedal firmly at the beginning of the brake zone and to ease out of heavy braking in order to concentrate on carrying more speed into the corner entry.

One thing I have learned about driving, it's like an onion. As you progress and get a feel for a skill, you peel a layer of experience off, and that reveals the next layer that you must concentrate on to master.

[24Chromium]

I was always taught, and in turn taught my students, that the best way to apply the brakes (in a straight braking zone) was to squeeze them at first in order to get the car to squat for best stability, then hammer them to threshold, gently easing off as you transition to throttle. The trick is to do all this in the least possible amount of time. I've yet to feel I've truly mastered this technique in my 15 years of DE driving!

[csmarx]

Here is a theory:

I've recently perused a PDF about the physics of racing, and while it gets a little too involved in the equations for my (MIT educated) brain, it does have some interesting conclusions and corollaries. For example in the chapter on why smoothness is important, we learn that given the car and it's suspension is really a spring/mass/damper system it likes sinusoidal inputs.

Hmm, I've always known that smoothness is important, but I never really thought that smooth doesn't necessarily mean linear! So I've been experimenting with doing sinusoidal-ish steering inputs, i.e. start of slowly and then accelerate the input to quite quick and slowing it down again as I reach full lock. Its quite amazing. If you have a heavier car with a soft suspension try this. With my wife's Prius if I do simple linear input going somewhat swiftly into a turn, it leans out of the turn and almost feels like it's going to topple over - despite being smooth about it. If I try the sinusoidal input instead, it's completely different! It kind of squats down, almost leans into the turn and is far more stable. Wow!

I have yet to try this on track, but I image that the GT3's relatively stiff suspension and stiffer low profile tires will make the effect less noticeable. It'll be interesting to see.

Now back to our regularly scheduled programming.

I'm wondering if braking isn't the same thing. It would certainly explain variations on the theme that one should start by a softer application of the brakes to get the car to settle before squeezing harder. Similarly the idea of getting off the brakes in a more gentle fashion after a hard application. In fact if you combine these two you get: first soft on, then hard, then soft off. It's basically sinusoidal!

Something to ponder.

-Christian

[FTS]

Good points Christian. Although I understand your points, IMO "smoothness" is not being smooth with your inputs but with the resultant behaviour of the car. Most pro drivers we see driving seem to have very jerky steering and other inputs, but as long as their actions result in smooth weight transfer through out the car, that is all that matters.

[beez]

It depends on what kind of corner it is, but in every instance, your first hit on the brakes should be your hardest, then you modulate as necessary. For tight corners being approached at high speed, that initial hit might be 80-90% or even all the way to threshold... for sweepers, this initial hit might be 25-30% or even just a brush, and longer duration. There are other factors that come into play as far as how much braking is needed - going uphill? Less braking is needed than you might think... long sweeper? The friction of the tires being being turned for that long of a time will help slow the car down, so don't over-slow the car on entry... I see a lot of people over-slowing their car for sweepers. BTW, threshold is not getting into the ABS, it's just short of it - without ABS, it's just short of lock-up.

But, the most important thing is you want to scrub-off speed of the mass of the car, but not kill your momentum doing so. In all cases, you want to use the modulation of the brakes to get the car settled back down onto the rear axle some - a good 10 feet or so - before turn in, so the car is balanced when you begin to turn the wheel for the corner. So many people concentrate on very late braking and corner entry speed, with most of the car's weight still on its nose as they turn in, which kills momentum. I see and coach many very late brakers who find themselves "parked" in the turn, having broken their momentum with this style of driving. Having the car more balanced at turn-in allows you to use super-light braking for balance, or trail-braking for rotation on the way to the apex, and a balanced car at the apex allows you to carry momentum through the corner, and get on the gas sooner as you exit. You can't get on the throttle early with a poorly balanced car. It's corner exit speed, not entrance speed, that makes the difference in gaining those tenths that are laying around the track waiting to be taken. The sensation of entering a corner fast can fool you into thinking you're making up time there, but you can only carry so much speed through the apex of any turn.

I guess I subscribe to slightly longer, and slightly earlier braking to keep the car more balanced. I used to be - as one of my coaches called it - a "scary late" braker, but I'm much faster doing it this way. My mantra: It's not how fast you go, but how little you slow down.

[beez]

Good points Christian. Although I understand your points, IMO "smoothness" is not being smooth with your inputs but with the resultant behaviour of the car. Most pro drivers we see driving seem to have very jerky steering and other inputs, but as long as their actions result in smooth weight transfer through out the car, that is all that matters.

I disagree - smoothness of inputs directly translates into smoothness of the car on the track. Often what you're seeing with in-car camera on pro drivers is them being constantly on the knife-edge - they are moving the wheel to make fast corrections that are necessary to keep the car on the road. Emulating this style while not having to make corrections because of understeer or oversteer conditions just wears out your arms and tires.

[Larry Herman]

I too fall more into the "ramp up the brake pressure" rather than the "hit it hard" technique, but for a few as yet unmentioned reasons. First, if you've ever driven an non-ABS car, you will appreciate the additional rear brake bias that you can run when you don't initially pitch the car on it's nose. Secondly, how "fast" you can actually ramp up the pressure depends on how stiff your car is. With a softer suspension like a stock GT3 has, you have to allow time (a few milli-seconds) for the front to dive under initial application. This will prevent excessive pitching and actually allow for greater initial braking. Even with full race suspensions, I have found it better to squeeze on the brakes rather than just pound on them. The more evenly you can keep pressure on all 4 tires the more grip that you will have, and the harder you can brake.

[FTS]

I disagree - smoothness of inputs directly translates into smoothness of the car on the track. Often what you're seeing with in-car camera on pro drivers is them being constantly on the knife-edge - they are moving the wheel to make fast corrections that are necessary to keep the car on the road. Emulating this style while not having to make corrections because of understeer or oversteer conditions just wears out your arms and tires.

Let me put it in another way. I define smoothness as getting the weight transfer to any part of the car as fast as possible just at the right time it is needed while staying on the optimum tire slip angles. To achieve this smoothness of inputs are irrelevant, actually abrupt inputs sometimes (or may be even often) are welcome. I am of course only stating opinion here and my understanding on how the theory should be translated into practice.

For example, we see pro drivers with very abrupt steering and throttle inputs, not to mention how they use the brakes. Nothing I see in vids can be classified as "smooth" driving from the input perspective.

So, if you are in a corner with increasing lateral Gs, which increases lateral weight transfer and vertical and lateral loads on tires, the slip angles of the tires will change and that change is constant. To manage to stay at the optimum slip angles that generate the most grip, you have to modulate steering and throttle constantly as well. That is why we see such rapid and abrupt steering inputs.

Similarly, the harder you accelerate, the more abrupt the throttle, when you lift off, the more weight will transfer to the front at a faster speed. If you do execute this at the right moment, the less brake you'll need to use. But again the input is not smooth, but the resultant action creates higher grip when needed and smoother output.

Of course this is all in my very humble interpretation of car dynamics and driving theories. :)

[Festina Lente]

^
Sprint racing you can beat the crap out of the car,

^
Endurance racing you have to be smooth, and preserve the car.

You'd better believe the latter are very smooth with their "inputs", otherwise the race is over early.

I think you need a session or two with Hurley versus some of the curb hoppers.

[lightweight]

This is a great discussion. I've always been taught that smoother is faster. An illuminating place to learn about braking and suspension response is on a motorcycle.

[beez]

Let me put it in another way. I define smoothness as getting the weight transfer to any part of the car as fast as possible just at the right time it is needed while staying on the optimum tire slip angles. To achieve this smoothness of inputs are irrelevant, actually abrupt inputs sometimes (or may be even often) are welcome. I am of course only stating opinion here and my understanding on how the theory should be translated into practice.

For example, we see pro drivers with very abrupt steering and throttle inputs, not to mention how they use the brakes. Nothing I see in vids can be classified as "smooth" driving from the input perspective.

So, if you are in a corner with increasing lateral Gs, which increases lateral weight transfer and vertical and lateral loads on tires, the slip angles of the tires will change and that change is constant. To manage to stay at the optimum slip angles that generate the most grip, you have to modulate steering and throttle constantly as well. That is why we see such rapid and abrupt steering inputs.

Similarly, the harder you accelerate, the more abrupt the throttle, when you lift off, the more weight will transfer to the front at a faster speed. If you do execute this at the right moment, the less brake you'll need to use. But again the input is not smooth, but the resultant action creates higher grip when needed and smoother output.

Of course this is all in my very humble interpretation of car dynamics and driving theories. :)

I guess I define smoothness as not unnecessarily upsetting the balance of the car. If you were to view the car driven by the pro drivers you mention seeing using very abrupt steering and throttle inputs from the outside, I guarantee you'd see a car that's twitching all over the road, not only side-to-side, and with weight transferring front to back as well. The main reason for not using abrupt steering and throttle inputs (both onto the throttle and coming off of the throttle) is you want to keep the weight transfers even, and as much in one direction as possible. For instance, when you come off the throttle very abruptly as you describe, you not only transfer the weight to the nose, but you can also have the car's front suspension "bounce" back in the other direction, garnering another transfer of weight at precisely the wrong time. The exception to this is when there's a dip or sudden elevation change where you might want to hammer the brakes as the suspension bottoms out to keep the suspension from bouncing on rebound, so the car stays settled. This will depend on how stiff-ly sprung the car is of course, and the rebound settings on the dampers... but in most cars, even race cars, there will some rebound from very abrupt release of the throttle. Side-to-side transfer of weight is the same thing - you only want to transfer weight once, if you can.

Some driving schools (I once heard that Jackie Stewart was a big proponent of this) use a car with a punch bowl bolted to the hood that contains a tennis ball on a string - the objective is to go as fast as you can while keeping the ball in the bowl.

I will say this - many times when you see in-car views of pros racing, they're doing these kinds of inputs because they're not on the line... when I'm doing W2W racing, and making passes, I'm spending a huge amount of time off the line in order to make headway through a lot of slower cars, or just trying to find a way around someone. Driving off the line, and in the klag, might necessitate these kind of inputs, but for fast qualifying laps or time trialing, a smooth transfer of weight, and keeping those transfers to a minimum is much preferable, and ultimately faster in my experience.

[NickW]

Smoother IS faster. What's also faster is keeping the wheel straight for as long as possible as opposed to having some steering input. And having little or to no toe either front or rear (keeps the chassis from binding, putting heat in wheel bearings creating hot spots).

I race laydown karts and road race sprint karts on big tracks, you had better believe steering input slows you down. Chassis setup is paramount for control. We watch everything from scrub radius to alignment almost every practice session- we can gain 1/10sec from more power, but literally a second or two if we can get closer to ideal chassis setup.

Of course all this is for naught if you can't drive... Smooth inputs at all times, smoothly to threshold braking, smoothly on throttle to WOT, smooth steering inputs to get into and out of corners quickly. Just because a car/kart can be darty does not mean that's how it's meant to be driven.

[FTS]

No doubt smooth is faster, but I am putting an argument as to whether the input or output need to be smoother, or are they the same?

[NickW]

Obviously if you stay within the traction circle you won't lose any traction, but to stay within that circle requires you to not exceed the chassis capabilities- those capabilities determine the size of the circle.

Ultimately we are concerned with getting through turns quicker, right? Instead of thinking of turns as brake-throttle input-turn in-track out-more throttle input, concern yourself with how to get to maximum speed as early as possible by track out. That usually means forgetting you have a ton of power, carrying far more speed into and thus out of the corner on a very stable chassis, and using far less brake than you thought you needed. I noticed my car is very neutral if the chassis is balanced, so if I don't give it any input via throttle, brake or steering the car is very settled and predictable. However, giving it throttle will lift the front, reducing the traction circle for the that end, and lifting the throttle will increase it. Braking will cause a more abrupt shift in weight transfer and really reduce the rear traction circle. So, if you are smooth on ALL your inputs you will always be able to maximize the size of the traction circle on the end of the car that needs it most. Now what you do with that traction, and whether you can use it to the limit, is another matter.

Of course, there are instances like in AX that you violate that concept to induce oversteer, but even AX requires a good pointy front end.

I'm sure I'm oversimplifying a lot of my concepts but the gist is there.

[csmarx]

No doubt smooth is faster, but I am putting an argument as to whether the input or output need to be smoother, or are they the same?

I think this is a truly excellent question!

The point of my previous post, which I didn't manage to state very clearly, is as follows: the car being a dynamic system of the spring/mass/damper kind, needs sinusoidal inputs in order to generate linear - i.e. smooth - outputs.

Sinusoidal meaning slowly initially, then accelerating to fairly quick, then decelerating input to the steering, the throttle, and in case of this thread, application to the brake.

I like this theory because it encompasses most of the comments from from different people, and it seems to work in real life too!

-Christian

[csmarx]

Obviously if you stay within the traction circle you won't lose any traction, but to stay within that circle requires you to not exceed the chassis capabilities- those capabilities determine the size of the circle.

Ultimately we are concerned with getting through turns quicker, right? Instead of thinking of turns as brake-throttle input-turn in-track out-more throttle input, concern yourself with how to get to maximum speed as early as possible by track out. That usually means forgetting you have a ton of power, carrying far more speed into and thus out of the corner on a very stable chassis, and using far less brake than you thought you needed. I noticed my car is very neutral if the chassis is balanced, so if I don't give it any input via throttle, brake or steering the car is very settled and predictable. However, giving it throttle will lift the front, reducing the traction circle for the that end, and lifting the throttle will increase it. Braking will cause a more abrupt shift in weight transfer and really reduce the rear traction circle. So, if you are smooth on ALL your inputs you will always be able to maximize the size of the traction circle on the end of the car that needs it most. Now what you do with that traction, and whether you can use it to the limit, is another matter.

Of course, there are instances like in AX that you violate that concept to induce oversteer, but even AX requires a good pointy front end.

I'm sure I'm oversimplifying a lot of my concepts but the gist is there.

You bring up a very important point which I often discuss with track newbies. I usually hear them excitedly exclaim that they were driving on the limit. I point out that "the limit" isn't a fixed quantity. A pro driver will drive the exact same car in a way that has a much higher limit. The point of learning how to drive isn't to get to the limit, but rather to first maximize the limit and then push to car to that limit. Which is what you are saying about expanding the traction circle by way of your driving.

The first time I went in a car with a professional racing driver, what was most striking wasn't how "exciting" it was. On the contrary it was how "calm" it all was - despite going incredibly fast. That was the first time I really got an insight into what smooth was, and how important it is to be even more relaxed the faster you go!

-Christian

[NickW]

Here is a theory:

I've recently perused a PDF about the physics of racing, and while it gets a little too involved in the equations for my (MIT educated) brain, it does have some interesting conclusions and corollaries. For example in the chapter on why smoothness is important, we learn that given the car and it's suspension is really a spring/mass/damper system it likes sinusoidal inputs.

Hmm, I've always known that smoothness is important, but I never really thought that smooth doesn't necessarily mean linear! So I've been experimenting with doing sinusoidal-ish steering inputs, i.e. start of slowly and then accelerate the input to quite quick and slowing it down again as I reach full lock. Its quite amazing. If you have a heavier car with a soft suspension try this. With my wife's Prius if I do simple linear input going somewhat swiftly into a turn, it leans out of the turn and almost feels like it's going to topple over - despite being smooth about it. If I try the sinusoidal input instead, it's completely different! It kind of squats down, almost leans into the turn and is far more stable. Wow!

I have yet to try this on track, but I image that the GT3's relatively stiff suspension and stiffer low profile tires will make the effect less noticeable. It'll be interesting to see.

Now back to our regularly scheduled programming.

I'm wondering if braking isn't the same thing. It would certainly explain variations on the theme that one should start by a softer application of the brakes to get the car to settle before squeezing harder. Similarly the idea of getting off the brakes in a more gentle fashion after a hard application. In fact if you combine these two you get: first soft on, then hard, then soft off. It's basically sinusoidal!

Something to ponder.

-Christian

For what it's worth that is the exact way I have to brake at T1 at Road America. The faster the speed, the more important you don't upset the car, especially if it's bucking like a bronco at 170mph!

[FTS]

Sinusoidal meaning slowly initially, then accelerating to fairly quick, then decelerating input to the steering, the throttle, and in case of this thread, application to the brake.

-Christian
Now that I have re-read your original post on this and this post, things are making more sense to me, at least this above statement is the first link, conceptually, between my chassis dynamics and driver training. Previously, I have not been able to link the two together in concept or execution.

My driving experience, as with most that replied to this thread, certainly collaborates this statement. My data also collaborates this statement. The part that is not collaborating or making sense to me is why would some professional drivers that I talked with advice me to be abrupt, especially under braking. The same thing happened during my recent PSDS visit too, which the coaches were in the camp of what Mr. Neil Roberts states.

There is no questions, I put out posts that are argumentative to generate discussion, but at the end I am trying to find out what is the next level of driving I need to be shooting for. I think the answer right now for me is the sinusodial approach (Christian, you should trademark the term "sinusodial driving" :-))) ); keep collecting data and analyze it until I can hit certain lap times while being absolutely smooth with inputs and observing the smooth outputs ::-/

Thank you.

[bman]

it was how "calm" it all was - despite going incredibly fast.

carrying far more speed into and thus out of the corner on a very stable chassis, and using far less brake than you thought you needed. I noticed my car is very neutral if the chassis is balanced, so if I don't give it any input via throttle, brake or steering the car is very settled and predictable.

I'm sure I'm oversimplifying a lot of my concepts but the gist is there.

I agree strongly with this! Carrying more speed through and OUT of a corner has much to do with the stability and balance of the chassis, in my experience. Easing of the brake a little earlier than I am comfortable doing, staying CALM, can actually result in a more stable entry resulting in earlier throttle application.

But......how you use the brake to achieve balance seems to vary depending on the corner. I'd love to hear opinions on when you want a flat chassis vs a loaded nose vs early throttle?

For some reason, I developed a bad habit of maintaining some brake pressure on ALL turn in's; a habit of trying to keep the nose down for good grip. But I'm fighting that habit and realiziing I've got to try different things.

T10 at VIR and T12 at Mid Ohio come to mind as examples of where I want straight line braking and off the brake early enough to insure a flat chassis at turn in. Both seem to have some postive camber at first and then flatten near apex.......so does flat apex = flat chassis??? If so, why does T1 at VIR seem to require a lot of trail brake? It has some positive camber on the entry but goes flat near the apex.... I assume it's because you're approaching at high speed, trying to maintain speed at long as possible with a relatively low speed exit? Yes? Or does it have more to do with the radius?

I understand a lot has to do with the car but are there any rules of thumb or opinions on proper chassis attitude relative to track surface (elevation/camber/radius)?

I like this thread, thanks!

[NickW]

But......how you use the brake to achieve balance seems to vary depending on the corner. I'd love to hear opinions on when you want a flat chassis vs a loaded nose vs early throttle?

That's a function of how large you need the traction circle to be at whichever end you need it at most.

For some corners like at Road America's Carousel, a long sweeping slightly downhill righthander that literally lasts 10 seconds or more, a neutral throttle will help keep the car in shape, a slight lift will tuck the nose back in (gain front traction from moving polar point forward plus camber gain from front end suspension compression that results from caster amount, PLUS a larger tire contact point at the front left wheel), and a slight acceleration will push the front a bit (scrub off lateral force if you've turned in a bit too much).

Again, I'm simplifying it quite a bit, there's a lot more going on- for example, LSD locking/unlocking, the rate at which it locks/unlocks, etc. But for the most part, I think I'm not too far off in concept.



For some reason, I developed a bad habit of maintaining some brake pressure on ALL turn in's; a habit of trying to keep the nose down for good grip. But I'm fighting that habit and realiziing I've got to try different things.

That's the worst thing you could probably do. Don't forget about the traction circle- the more traction you use for braking, the less you'll have for turn in. You may be expanding the circle by getting on the brakes, but the effective turning traction is probably severely limited. You have to ask yourself- which is more important- braking or turning in, and divvy up the circle accordingly.

Brakes on a racecar (or street car on the track) are not for actually stopping- you never want to actually stop. Brakes are for modulating speed- a tool to get the car to behave the way you want it to BEFORE you get to the apex. I've noticed that most people tend to overbrake because they thing threshold braking into corners is the fast way- probably read it in books, but never really properly taught by someone. The function of threshold braking is far more difficult to execute CONSISTENTLY- you may be able to do it 20% of the time, maybe even 70% of the time, but to drive effectively on the track you have to learn to execute each action as close to 100% as possible. Most people I know who threshold brake to the apex (like what they teach in the Skippy books) are incredibly bad at it, tending to overly slow down their cars- you can hear their mistakes when they release the brake and get on the throttle very abruptly. Even the pros make mistakes doing this- every time you see a racecar go straight and miss the apex, the driver is probably fighting braking forces (getting the car slow enough to get within his turning traction circle).


T10 at VIR and T12 at Mid Ohio come to mind as examples of where I want straight line braking and off the brake early enough to insure a flat chassis at turn in. Both seem to have some postive camber at first and then flatten near apex.......so does flat apex = flat chassis??? If so, why does T1 at VIR seem to require a lot of trail brake? It has some positive camber on the entry but goes flat near the apex.... I assume it's because you're approaching at high speed, trying to maintain speed at long as possible with a relatively low speed exit? Yes? Or does it have more to do with the radius?

I understand a lot has to do with the car but are there any rules of thumb or opinions on proper chassis attitude relative to track surface (elevation/camber/radius)?

I like this thread, thanks!

I can't comment on T10 at VIR, it's been many, many years since I raced either course there and never the full course. At Mid Ohio T12 in a kart is a throttle breather- maintenance throttle before turn in and back to WOT before T13. In a car I would say that corner is a bit tricky because of the subtle off cambering of the turn (track falls away from direction of turn). The other thing to note at T12 is you have to give up some of the track out for the turn in for T13, which again you give up some of the track out to get a good run onto T14 and the main straight. If you construct your corner exits taking each turn in reverse you will usually end up with a more ideal line (at least that works for me).

[bman]

Thanks for the feedback! I am with you on long sweepers and threshold braking.

In my experience, T12 at Mid Ohio is indeed tricky if you hold the brake as you approach the apex. As you describe, the track flatens and falls away but has positive camber on the approach. Keeping the front end loaded with the track falling away equals

pLXIyiCfTmo

For me it's best taken with straight line braking, off early, settle, touch of throttle and all is good.

how large you need the traction circle to be at whichever end you need it at most.


Can you elborate?

I can't imagine the braking in a kart can compare to a GT car at Mid Ohio but what do you do in Keyhole and Carousel?

I find my chassis has the best balance if I apply LIGHT brake at initial turn in and hold the same pressure half way to 2/3 through the corner.....basically braking and turning together but very gently and with steady arc'd steering. The tough part is in not applying too much initial brake and trusting that I can maintain constant pressure and the car will arc smoothly.

[NickW]

Can you elborate?

I can't imagine the braking in a kart can compare to a GT car at Mid Ohio but what do you do in Keyhole and Carousel?

I find my chassis has the best balance if I apply LIGHT brake at initial turn in and hold the same pressure half way to 2/3 through the corner.....basically braking and turning together but very gently and with steady arc'd steering. The tough part is in not applying too much initial brake and trusting that I can maintain constant pressure and the car will arc smoothly.

At the Keyhole we go to threshold brake immediately (braking in a straight line after the chicane), then turn in after braking is complete, apexing twice around the turn, riding the concrete patch for the most traction. Throttle application is immediate because the chassis is settled (unlike a car), increasing the throttle as long as the front end stays planted in the right direction (no lifting). Track out to the runout patch on the left, straightline the track from there to the turn in point at T5 (coming across the track near the emergency lane on the right).

The Carousel at M.O. is tricky because of the big bump in the middle of the apex. That tends to separate ribs if you're not careful. We tend to go through T12 hot, flatfoot on the throttle, then brake in a straight line right before the turn in for T13, double apexing it as opposed to a single apex specifically because of the bump. End result is you lose .1 second on that corner, but you keep your ribs intact, and since T14 comes up quickly, the speed you lose through T13 actually helps give you time to set up for T14.

I should be there in two weeks for the WKA National. I can get some on kart footage and post it if you want.

[csmarx]

In my experience, T12 at Mid Ohio is indeed tricky if you hold the brake as you approach the apex. As you describe, the track flatens and falls away but has positive camber on the approach. Keeping the front end loaded with the track falling away equals

pLXIyiCfTmo



Wow, what a fun looking track with some challenging turns and lots of elevation change. Too bad it's so far from CA!

IMHO the guy lost it primarily because of the brow he was going with too much steering lock on. To make matters worse he seemed to apply the brakes as well.

I was taught to momentarily straighten the steering when going over brows in a turn. It unloads the tires for a moment until the car settles again on the other side of the brow. It's the short version of making it a double apex.

-Christian

[csmarx]

NickW, could you comment on the difference between driving karts and cars. It seems that a lot of your racing experience is in karts, but in limited experience with serious karts I found them to be completely different to drive. The main difference being that karts don't really have a suspension, so the weight transfer happens much more quickly than in a car suspension. I was driving kart without a rear differential, so you really had to use the brakes to lift u the inside rear wheel to get the kart to turn in. You pretty much had to do a slight amount of trail braking into most turns.

But I'd love to hear your thought on the differences ihow you have to drive these very different beasts. It's a bit like driving a front wheel drive vs rear wheel drive. You use the throttle with quite different effect in turns. but what about karts vs a Porsche?

-Christian

[NickW]

Christian-

I can probably discuss this on another thread, that is quite a bit off topic and although some of my posts have been on the periphery of the subject, a discussion just on karts and karting dynamics probably isn't appropriate.

There are some things that apply though- my discussion on the traction circle and how it expands/contracts depending upon polar moment and weight bias, etc. The concepts are very similar and in some cases even magnified- you learn very quickly what is and isn't important in setup and driving.

[FTS]

a discussion just on karts and karting dynamics probably isn't appropriate.

I cannot think of any discussion that is inappropriate for this web forum, except the usual stuff. Discuss all you want please.

[bman]

the big bump in the middle of the apex. That tends to separate ribs if you're not careful..

I can get some on kart footage and post it if you want.

I know what you mean! It's pretty nasty in a car and can only imagine how rough it must be in a kart.

Yes, please! I'd like to watch.

Wow, what a fun looking track with some challenging turns and lots of elevation change.

I was taught to momentarily straighten the steering when going over brows in a turn. It unloads the tires for a moment until the car settles again on the other side of the brow.

It's a blast to drive! I would strongly recommend it for any track junkie. It's also, IMO, a track that will test your braking skills. It requires several techniques; if you want to be quick ;)

Check out the turn before the spin, turn 11. It's exactly the type of turn where you need to open the wheel as you crest a "brow". It's awesome!

I've only been to Mid Ohio twice, most recently last month. It's such a unique and fun track that on my 7 1/2 hour drive home, which is normally a drag, I found myself smiling, seemingly for hours, as I reflected on the weekend. I can't recall ever doing that before :D

[beez]

The Boxster spins because he/she is braking too hard with too much steering input - too much traction on the front, while the rear has hardly any weight on it. Look at the attitude of the car as it begins to enter the corner - it looks to me the driver thought they were carrying too much speed into the corner, and tried to fix the situation with progressive braking - adding more pressure as they continued to turn the wheel - look at how fast the car with the camera in it catches up to the quickly, and progressively slowing Boxster. Unfortunately the back end also gets light because of the slight crest in the middle of the turn - this exacerbates the situation. but the spin actually begins before the elevation change.

IMHO, one needs to use very different braking techniques for each kind of corner... if you're trying to threshold brake at each corner, no matter it's configuration, then you're using your brakes too much, and probably over-slowing the car in many instances.

[NickW]

Mid Ohio and Grattan are the two most technical tracks in the Upper Midwest and the most fun to drive. I would put either of those up there with Barber, Road Atlanta, and Laguna Seca as technically difficult to master AND fun to drive.

There are other tracks here too within a 4 hour radius (that I have run), GingerMan, Putnam Park, Waterford Hills, Blackhawk Farms, Autobahn Country Club, Mikwaukee Mile etc. but those are either not that fun or not that difficult. There's a little known "favorite track" to some old time F1 and Indycar pros called Meadowdale Raceway that is defunct too. Fun stuff...

[FTS]

With all this discussion, I am pumped up, I am going to VIR again today! :D

[FTS]

VIR was awesome. Mercedes/Audi/BMW clubs had the Marque Madness event, They were very kind to accept me for Friday, and weather was perfect. They really put out a great event, there were may be 45-50 cars, so we got a lot of track time, nearly 3 hours.

More importantly, I got to test a lot of what has been talked about in this thread. One distintictive conclusion I reached is my biggest problem is not how apply the brakes, but how I release them. I worked on that specifically, to release the brakes without upsetting the balance of the car, and I think during my 4th and 5th sessions, I could consistently do so at every corner. I am not sure if I was any faster, but the car and I were cooperating much better :)

[bman]

VIR was awesome.

how I release them. I worked on that specifically, to release the brakes without upsetting the balance of the car

I thought you were kidding about heading to VIR yesterday. You just went down for the day? You've got a problem! :-8

What change did you make in the release? Earlier? Which corners in particular?

Also, did you try different lines and braking thru T3?

[csmarx]

(Christian, you should trademark the term "sinusodial driving" :-))) )

Hey, if I could make a living from any kind of driving instruction I would! :p

[FTS]

I thought you were kidding about heading to VIR yesterday. You just went down for the day? You've got a problem! :-8
I never kid about VIR, and no doubt I have a (or more) problem(s) :ROFL!:

What change did you make in the release? Earlier? Which corners in particular?

Also, did you try different lines and braking thru T3?

Actually I was releasing a tiny bit later, but gentler, especially in T3, T4 and T10. I tried your line in T3, which worked better in entry, the car was more stable and controlling the brake pressure was easier as I broke slightly earlier with less pressure and I could more consistently take the turn. The preliminary result of doing so is... I am not sure what the word is frankly; I was significantly slower in entry, but slightly faster past the apex. The significance of this is that the conditions were much less favorable than in March or May; it was between 100-105 deg heat with very high humidity, the track was very greasy in many corners, all corners generally lacked grip, top speeds were also lower by 3-7 mph. Even so, my best was 2:11.7 in the morning, when it was about 92-95 with moderate to high humidity.

There is much more to look at in the data before any real results can be drawn, but I love that stuff and I have quite a bit of data to play with :D

I might put my notes in another thread as I look at data.

[mdrums]

When I hired Chris Hall for coaching at Sebring he told me after a few laps with me that I'm the last of the late brakers...he could not believe how deep I got the Carrera into the brake zone. He said this is not the way to go fast and take car of equipment. Slamming on the brake as late as possible on every turn is wrong and Chris drove my car and proved it. Also there are some turn were you get off the brake early and balance the car and sail it into the turn and then get on the throttle. My whole lesson was about brake release and modulating after he got me to brake slightly earlier and softer. I can't wait for some more lesson later this year.

[FTS]

I certainly do agree with Chris, not that my word counts for anything against his :), but what is the most important thing is the confidence of the driver and the feel s/he has. Slamming the brakes at the very last possible moment never felt like a solution to me, at least with street cars; the situation may be different with race cars with heavy aero.

[NickW]

So last weekend I tried to shake off the rust and go racing at Mid Ohio.

The driving part was fine. Unfortunately the chassis and engine tuning side of it was a complete disaster. Things started to click inside my head about 24 hours AFTER the weekend...

As the saying goes, there's a race happening, I'm just not in it.

http://contour.com/stories/wka-mid-ohio-tag-2-2011

The race line is still appropriate. If you watch and listen closely in the video of the lap, you will be able to tell the chassis is binding up in the rear on track out from the apex, putting me 30 ft down on the competition every lap in the tighter corners, and that the kart probably has too much Ackerman causing the turn in looseness.

[FTS]

It is pretty amazing to see this level of action this close to the ground. Setting up a kart is really complex I think, although I have NO experience with it, but without any springs/shocks, it is all geometry and probably millimeters of adjustments.

[Skypalace]

Very interesting discussion.

My personal answer is that it depends on what the purpose is, of the session and lap. For all-out qualifying, trying to get every last hundredth (I just had a race weekend where top three of us were within 23 thousanths of a second in qualifying), then going from full throttle to full brakes is quickest, IF 1) you don't end up over-slowing and killing your mid-corner and thus exit speed, as is VERY often the case when using max brakes, and 2) you don't lock up your brakes (on a non-ABS car).

On a race pace, I'm usually (but not always) a little less aggressive in braking zones, I brake a little earlier and a little less hard, to reduce chance of lockup and give more room to increase braking if needed to make the corner. Depends of course on the competitive situation, am I chasing someone or forced to defend, or am I in a 'comfortable' position where keeping up a pace is all that's needed to prevent a position change.

The over-braking is what most people end up doing if they're trying to 'banzai' the braking zone, so that's why it ends up being better not to apply the brakes too hard - it lets them modulate their overall speed easier. At full near-lockup braking, any GT/Cup car has such amazing brakes that the speed comes off at a very prodigous pace, and it's very difficult to stop braking at the right point. Also, if you're aggressively braking, and you brake even a little too early, you need to reduce the braking forces a fair bit later in the braking zone to prevent over-slowing. All of this is much easier to control at lower braking levels, which I believe is why it's often faster (and certainly safer) to brake less. However, if you're getting off the brakes at the right time, and you're not locking up, simple physics says you want to be on the gas as long as possible, then on the brakes as late and hard as possible, to maximize your speed over every foot of the course. Not very easy for us mere mortals to do, and the additional time gained by late/hard braking is usually overwhelmed by the time lost in having too low a mid-corner and thus corner exit speed, killing speed all the way to the next braking zone.

I've learned a lot about braking while going from an ABS car (996 Cup) to a non-ABS car (997 Cup), with manual bias control. I've had to adjust my braking to trail-brake less and get more braking done before turnin, or I was regularly locking up the inside front wheel late into the corner. This actually caused me to change my lines somewhat.

In the wet (just came off a weekend with 5 wet sessions), I'm of course easier on the brake application, as I'm always sensing for traction, including under braking. Downshifting is less aggressive also (lower in the rpm range) or it'll cause rear lockup (in both 996 and 997 I use downshifting/engine braking to augment the car's rear braking).

Many drivers seem to want to maximize their braking, and brake as hard and late as possible. If they have data or video, I often see much more time to be gained in better controlling getting OFF the brake, and rolling through the corner as quickly as possible, and back onto the throttle as early as possible, minimizing time through the corner and all the way down the next straight. There's often a full half-second or more available there from a single corner, versus perhaps a tenth by braking a little harder and later. So yet another reason many instructors/coaches want you to concentrate on areas other than braking as hard as possible.

Final thought - for DE drivers (I instructed for many years but haven't lately), the goal is to get drivers safely around the track, on a good line, slowly increasing their speed as they approach the limits of their cars and their own abilities. It's way to easy to exceed the abilities of driver OR car by nailing the brakes hard, and lots of bad things can happen, as the start of a braking zone after a long straight is the fastest the car is going. I strongly believe (both in DE and in racing) in gently approaching limits from underneath them, and I've too often seen bad things happen in DE from things like mid-corner throttle lift from someone carrying more speed than they're comfortable with, or seeing something ahead that they're not comfortable with, even though their car can handle their current cornering speed.

Next topic: pinching exits, why do I see SO many drivers keep full (or nearly full) steering input well after apex, while applying full throttle, and not unwinding the wheel and going all the way to trackout? Have seen so many incidents... Another topic though :-)

[FTS]

What can I say, an excellent first post; welcome to the community Jim.

I certainly agree that the physics of vehicle dynamics dictate maximum braking for the shortest period of time and being on throttle for the longest periods is the fastest possible way around any circuit. The theory goes out the door when the human starts making the decisions; we are not consistent and most often not rational either.

What I find interesting and something that I would not have thought about is how you had to change your braking to use less trailing with a non-ABS car. It does make sense, I just would not have thought that might be one of the outcomes.

I have been watching F1 since 9-yrs old, that's over 30 yrs btw, and what grabs my attention the most is how seldom those drivers brake on a straight line. Granted they have significant help from their aero, but being on such balance and sensitivity is something to be admired I think.

I like your next topic as well, I hope you do start the thread ;)

[Skypalace]

Thanks! Re F1 drivers, certainly they need to brake in non-straight lines, esp. at say Valencia today where they're almost always in a corner.

Now I think I understand better why they're constantly adjusting brake bias - moving bias rearward will let them trailbrake deeper into a corner before locking up. Too far rear though and esp. earlier in the braking zone you might lock up the rears, that's much worse. So at least for mortals like me, I err on the side of front brake bias, better to have front lockup and understeer through a corner entry, than to have the back step out when under any side loading (esp. entering a high or medium speed corner) and swapping ends (spin at best, into something hard at worst). Though if I'm never getting any lockup on the data (easy to see from logging of the four wheel speeds), then I'm just not braking hard enough, I do want to see a touch of lockup at max braking, just minimal (one wheel slowing a little, never full lock) and fairly even front to rear :-)

I did expect to take some time adjusting to non-ABS, I didn't expect to have to change lines etc. either. I honestly didn't realize (except now in retrospect) how late into corners I'd been trail-braking, and how often the ABS in my 996 must have been keeping the inside front wheel rolling.

So I definitely pay attention to braking, but as with the 996, most of the time I make up when improving lap times is in carrying more speed through the corner (ie. getting off the brake earlier), and getting on the gas earlier.

[NickW]

It is pretty amazing to see this level of action this close to the ground. Setting up a kart is really complex I think, although I have experience with it, but without any springs/shocks, it is all geometry and probably millimeters of adjustments.

The setup is magnified by the type of racing- road racing a kart is really a study on not only driving ability but also setup- both are required to be competitive. What's really important in road racing is- you can't win the race in the first corner but you certainly can lose it there. The races are 30-45 minutes long and if the track is bumpy you'll get worn out quick.

If you watch the video closely you'll see that on the back straight I peak over 90 mph (92 to be exact) according to the GPS, and take most turns about 70mph. Some people would say that karts don't have to slow down much for turns, but the inverse is true too- since everyone is trying to slow down the least (because we all want to win) it's a dogfight. To put it into perspective, laptimes in my situp class should be around 1.38.xx at Mid Ohio. That's a kart with a water cooled 125cc two stroke, no gearbox, disc brakes in the front and rear. Sit up Shifters are about 7 seconds faster, laydown shifters even more so.

There's no ABS, no traction control, no power steering. If we have Tillotson carbs we can tune the needles on the fly, if it's a Keihin/Mikuni/d'Ellorto then we have to watch the weather station like a hawk and put the right jets/needles/tubes in. We check chassis alignment three or four times a day, and change alignment/setup throughout the day to keep up with the track conditions.

Brake bias is adjustable on the fly- however, i don't know too many people who use it unless there's something quite a bit wrong. Karts are rear biased- rear locks up before fronts, because the rear tires are bigger (bigger contact patch), weight is rear biased, and the fronts are useless if they lock up first (neither brake nor directional control). Because the bias is rearward, you learn to really carry speed through the turns- threshold braking while turning marginalizes the brake AND turning ability, probably either sending you off spinning or over slowing the turn- basically , if you can threshold brake into the turn you're not going fast enough. At least, that's how it works in karts.

In cars it's a different story because there are a lot of engineered aids- brake bias is computer controlled... ABS, TC and SC intervene with most "optimistic" input... Steering rack ratios are overly slow requiring a lot of input... And engines are so tractable that you are rarely out of the power band (unless you're really goofing up) which covers up a lot of mistakes. Basically, modern cars are much easier to drive fast on tracks than cars from even as recent as 10 years ago.

[FTS]

I think you did catch my big mistake in my sentence; I meant "I have NO experience" in setting up karts :)

Your explanation on kart setup is precisely what is so difficult in driving karts competitively IMHO. Thankfully, it is a smaller vehicle and getting on a table/jacks is easier to make setup changes, but you really need to understand the geometric options, which are finite of course. At the same time, not having the help of shock/spring settings makes the whole thing even more difficult.

Do you use A/R bars on karts?

And driving... OMG, I cannot imagine working within a window of 20 mph; each 1 mph, or even 0.5 mph, must count. So, if you brake 5 ft too early or too late, you can either loose a spot or race, or worse, find yourself moving the lawn. Amazing.

[NickW]

I think you did catch my big mistake in my sentence; I meant "I have NO experience" in setting up karts :)

No big deal. Everyone has to learn from somewhere. There are lots of people far more experienced than me. I've only been racing karts for about 7 years.

Your explanation on kart setup is precisely what is so difficult in driving karts competitively IMHO. Thankfully, it is a smaller vehicle and getting on a table/jacks is easier to make setup changes, but you really need to understand the geometric options, which are finite of course. At the same time, not having the help of shock/spring settings makes the whole thing even more difficult.

Do you use A/R bars on karts?

Kart setup is not easy.

First and foremost is seat position. That determines pretty much everything (because the biggest lump on the kart is the driver).

Front end setup can be separated into different ways- ride height, stiffness, and alignment. Ride height determines front end jacking, stiffness can be adjusted with a removable bar between the front yokes, and alignment determines camber, castor and toe. There is also track width, hub stiffness, wheel width and steering Ackerman to consider.

Rear end setup is determined by ride height (axle height on most karts are adjustable), axle stiffness, where and which bearings are "locked in", hub stiffness, wheel size and stiffness, and track width. There is also a removable bar in the back that determines chassis twist.

Then there's the kart chassis midsection which determines transient response from front to rear- most chassis' have a removable fourth rail that goes from the midsection to the back, and the front tray can be tightened/loosened according to what the needs are. Not to mention seat stays (adding, removing, loosening, tightening)...

Those are the basics... if you can get a handle on those you're doing better than me!

There are no antiroll bars on karts. Antiroll bars are transient torsion springs that connect the left and right suspension- they are a tuning aid and ideally should be as soft as possible if not disconnected (I know that is a controversial statement), corner spring rate and suspension geometry should determine roll. On my GT2 I have to use them as a bandaid for a conservative setup- the car pushes everywhere. With a more aggressive setup coming (springs, shocks, alignment) I hope to be able to back off the bar settings to get more bump compliance (curb crashing).

For karts you should think of the entire chassis as a giant spring, and compliance for what you want it to do is managed on a micro and macro level. If you get a good handle on how to tune a kart chassis, tuning a car is not much more difficult. Ultimately you need to think about how to work on the end that needs improvement and not take away from the one that works.

And driving... OMG, I cannot imagine working within a window of 20 mph; each 1 mph, or even 0.5 mph, must count. So, if you brake 5 ft too early or too late, you can either loose a spot or race, or worse, find yourself moving the lawn. Amazing.

Oh yeah! That's what makes it fun (or in my case that weekend, a lesson in futility). Losing 30 ft every tight corner means just keeping up is a W in my book. I'm planning on going to Grattan in a few weeks, let's hope it's better. Check out Grattan if you want to see a crazy track!

edit-

Actually, I was thinking about the "20mph window"... it's actually less than that. Top speed is a given- if you can't keep up you're out to lunch. So the relative operating window is actually your cornering speed- entry, apex and exit speeds. That is probably a much smaller window- 2 to 3 mph at most if you're competitive. It's the same in most motorsports- relative speed differences usually determine the outcome.

[FTS]

Well, this has been a great schooling for me, and I truly appreciate it. It is fascinating to me, chassis setup that is. I used to be involved with it in stage rally cars, which I thought was difficult, but karts are much more difficult based on the details you so graciously provided. We basically played with shock setup (travel/bump/rebound), ride height, springs, wheels/tires and roll bars; other than that, we left it alone.

Thank you for the details Nick :pals:

[bman]

Next topic: pinching exits, why do I see SO many drivers keep full (or nearly full) steering input well after apex, while applying full throttle, and not unwinding the wheel and going all the way to trackout? Have seen so many incidents... Another topic though :-)

I am surprised how often I see this and it's scary! I can understand a beginner-intermediate driver doing it but I've seen it too often with intermediate-advanced drivers. Moreover, I have found a resistance to change when you point it out. I've found myself practically begging drivers to "OPEN THE WHEEL", lap after lap. And often the response is "WHY?"....You really get concerned when this happens because you worry the driver has limited feel/sense of what's going on.

I think it is applicable to this braking discussion because often it's a symptom caused by over braking and early release of the brake. The driver isn't rolling into a corner, so they're on the throttle too early.

[NickW]

I also see a lot of exit pinching. What I've noticed as a beginner's symptom is usually apexing too early. Many overly enthusiastic novice drivers begin their turn in too soon. You rarely see this problem with a late apex turn in- those drivers usually have too little speed into the turn and also too much space on track out from the apex.
The other problem I see with many drivers is not getting the wheel straight early enough- or taking too much time turning.
Another symptom is the "threshold to the apex" braker who overestimates his/her traction circle, usually missing the apex completely and thus also flying off the outside of the track exit.
When I instructed (and am about to start for the Chicago region PCA soon) I used to tell students to literally try to hit every cone on the track. I would estimate how much they were off, and encourage them to really aim for the cones on the track, thus demonstrating how much they were pinching their turn in and track outs by not using the entire track.
Teaching students how to read a track is the best lesson for them.

[Skypalace]

Here's how I (used to when I instructed) explain releasing the wheel on exit.

I explain that there is always a limited amount of traction available, and the goal in a corner is to always use all of the traction available. So you brake fully, but have to start releasing the brake as you turn in, to 'release' traction so that you can start using it to turn. When you're at apex at max turnin, you can't be on the brake or throttle as you're using all your traction to turn.

When you want to start accelerating from the apex to track out, you need to 'release' traction to make it available for acceleration, and you have to do this by releasing the wheel as you slowly apply the throttle. By the time you're on full throttle at trackout, you have to have fully released the wheel, or you won't have sufficient traction!

I also do a visualization exercise - think of a string tied between your toe and the steering wheel. When you're on full braking, string is all the way tight from the bottom of the wheel to your toe. As you turn, turning the wheel will lift your toe on the brake. As you press the accelerator after exit, think of it pulling the outside of the steering wheel back down, so that you have to accelerate.

I think that many novice and intermediate drivers are scared of getting too close to the trackout, as they're worried about getting onto (or over) the exit curbing. After all, their instructors have told them numerous times about bad things happening when they drop a wheel off the outside of a curb on exit. So in response they're staying away from track out, but their mechanism for doing so isn't doing a trackout to a lesser point, it's to keep full steering input in while exiting the corner, which at best delays their throttle input until they're pointed straight (killing their corner exit speed), or at worst adding throttle with full input, potentially causing spins or worse (exiting track when overcorrecting after attempting to catch a spin for example).

Jim

[Larry Herman]

I certainly agree that the physics of vehicle dynamics dictate maximum braking for the shortest period of time and being on throttle for the longest periods is the fastest possible way around any circuit. Fatih, why would you think that?

[FTS]

Hmmm, seemingly a simple question, but this one really made me think Larry :) Am I making an assumption that may not be correct?

Fastest way through a circuit is, or should be, shortest distance while having the longest time periods on the throttle, which means shortest time on brakes, which requires maximum braking needed, no more, for the car to go through the corners. What am I missing?

[beez]

To me, the fastest way around a circuit is the compromise between covering the least amount of real estate while turning the steering wheel the least. if you can accomplish that, then the very fastest way through the turns, will be self-evident. this will set you up to give you the longest possible time on the throttle in the straights.

[Larry Herman]

Momentum. The fastest way through a circuit is with the highest average speed. If I can brake longer & more gently to allow my car to have better balance and therefore more lateral grip, I can keep my overall speed higher, resulting in a faster corner and ultimately a faster lap. There are some corners where this technique yields higher mph at every point in the corner segment. There are other turns where it may not. The skill is in knowing the requirements of each corner, not applying a blanket driving style across the board. That is why we coach using data; to figure this out.

[NickW]

Hmm... kind of a loaded question...

I touched upon this at rennlist- http://forums.rennlist.com/rennforums/racing-and-drivers-education-forum/641274-brake-rotors-and-pads-help-2.html

But the issue isn't even as simple as keeping momentum up.

As a driver's experience progresses, car setup changes. A beginner will probably prefer a tighter car- one that pushes. That way the worst possible thing he can do is just push off the track if he holds the throttle too long. As the driver gets better with actually controlling the car, the setup will get looser, and become more pointy. How the car is driven changes.

In general, as the movie quote goes, loose is fast. But just because loose is fast doesn't mean everyone can drive such a setup. A tight car won't want to "dance" but a loose car will quickly tell you you're not in charge if you're not on top of it.

If you're really intent of improving as a driver, making setup changes throughout the day will really help you understand chassis dynamics. Get outside your comfort zone, but don't drive beyond your ability. In general, when I see someone off the track or looping it, I think- driving beyond ability.

EDIT-

I attached a pic of me at Road America, T5. You can see the cone on the gator strip, and my tires within 3 feet (probably less) of that edge. In addition, you can see by the way my car's weight is jacked to the rear right corner that I am accelerating through the corner- all braking finished way beforehand. That is what they mean when they say "slow in, fast out."

[Larry Herman]

Get outside your comfort zone, but don't drive beyond your ability. In general, when I see someone off the track or looping it, I think- driving beyond ability.This is probably getting off-topic, and maybe worthy of another thread, but I see plenty of people looping it and going off-track due to poor technique and lack of car feel. It's not that they are being too aggressive as much as how they are driving causes the car to go from 8/10ths to 11/10ths instantly, and beyond their ability to recognize it. I am firmly convinced that barring an improperly setup car, there is no such thing as a snap-spin that "just happened". The situations that can result in that type of car behavior are predictable and recognizable. Then again, maybe that is precisely what is defined as "driving beyond ones ability".

[NickW]

This is probably getting off-topic, and maybe worthy of another thread, but I see plenty of people looping it and going off-track due to poor technique and lack of car feel. It's not that they are being too aggressive as much as how they are driving causes the car to go from 8/10ths to 11/10ths instantly, and beyond their ability to recognize it. I am firmly convinced that barring an improperly setup car, there is no such thing as a snap-spin that "just happened". The situations that can result in that type of car behavior are predictable and recognizable. Then again, maybe that is precisely what is defined as "driving beyond ones ability".

Well, I think part of the problem is how HPDE teaches people how to brake- usually an A/X brake zone exercise. That does nothing to actually promote feel of the braking, although it teaches the student that they have powerful brakes. If anything it teaches students they can be hamfisted in their input.

Skill requires sensitivity. If you can't sense it how can you react to it? I had a related issue with a friend recently- he insisted on turning up the radio in the car, and I kept telling him I couldn't drive the car properly without hearing the engine (manual trans). He doesn't drive stick. Can you see the problem- we can't relate because our POV is so different- and that's part of the problem with a lot of beginners- they want to go fast on a track, without the associated learning and experience. As for my friend, I told him he needs to stick to his Lexus... :)

[Skypalace]

Saying that the fastest way around a course is the highest average speed is a bit of a tautology - average speed is of course course distance divided by time, the shorter the time the higher the speed. Course distance is (relatively) fixed.

Any of these fine suggestions above are rules of thumb, but are never perfectly correct. The fastest way around a course depends on a lot of variables, and is extremely car-dependent, as well as course dependent.

The best line through a particular corner very much depends on what's after the corner. If there's a long straight, then the best line will likely have a very late apex so that you can get on full throttle as quickly as possible. But if there's another corner immediately thereafter turning the same direction, you might do a very early apex to be able to get you to the outside edge of the track as quickly as possible to set up for the following corner, which might be more important.

Then there are corners with a broad range of lines, turn 7 at the (repaved) Portland International Raceway is an example, it's 6 or 8 cars wide, but leads onto a the long back straight. Sure you want a late apex in order to maximize exit speed onto the straight, but it's SO wide on entry that I see many people enter too wide, adding material track distance at the slowest corner on the course, adding time that they don't need to add as it's not actually improving their exit speed. Also, as with many corners, the line through there is very different on a momentum car (944 or Spec Miata) than in a car with significant power, as you normally need a later apex in a higher-powered car so that you can be on full throttle without rear tires getting loose (ie. you have less available grip for lateral acceleration). With a lower powered car, there's less traction required for acceleration on full throttle, and thus more available for lateral grip (turning), so you can apex earlier and continue turning but still have full throttle through the exit.


And of course, on almost any corner a 911 wants a later apex than a Vette with equivalent power, because of the rearward weight bias, and a late turnin works because trail braking allows you to rotate that big pendulum behind you, whereas a car with 50/50 weight distribution won't react to trailbraking the same way.

I completely agree with Nick on sensitivity. It's one reason I've been having braking problems with the new Cup - the brakes are rock-hard, like pushing against a brick wall, and have very little travel, and virtually zero feedback through the pedal. I'm basically having to calibrate how hard my quads are pushing the pedal, rather than feeling the pedal travel through the side of my foot through my driving shoes, like in the 996 that has a softer pedal and much more pdeal travel during braking. I'm developing the feel, but I'm not fully there yet (or I wouldn't have spun under braking twice in my last race weekend :-))

I like to drive with my bottom seat cushion removed, as it gives me better feel of the car - literally improving the feedback through the seat of my pants. The biggest difference in being able to sense yaw (esp. rear of the car moving out) as quickly as possible. With hard engine and tranny mounts, there's enough engine & tranny noise in the car (plus I have earpieces in) that it's difficult to hear the tires, which are a ton easier to hear in a street car.

I also have a seat with very high side (thigh) bolsters, in a seat that most people would probably consider to be one size too small, but I like to have zero movement in the seat so that I can feel the car as much as possible. I like to think it's one reason I'm much better in a real car than in video games. As Nick says above, loose is fast, I definitely prefer a car a little on the loose side, but it requires high sensitivity (but it's SOOO fun when it's working!). I spin fairly often in video games because I can't sense the yaw movement of rear getting loose, in a game the only way to sense yaw is through the front windshield, but that's definitely not how I sense it in a real car. Or so I like to think :-)

I have full Motec data in my cars, and spend a very bit of time analyzing it, to see exactly what works and what doesn't. Often it's counter-intuitive. I've seen many times where I've changed a line to make up .3 sec on corner entry, only to lose .5 second through to the next corner. I've also seen the other way, lost .3 sec on corner entry, and made up .5 second along the next straight. Data is very helpful, but it takes some practice to figure out how to use it properly, and to actually help yourself rather than confuse yourself with so much information.

I find video even more useful, I will never pass up an opportunity to have someone look at my video and make comments. I've had many pros and fellow competitors (most helpful if they're in a different class so not directly competitive :-)) willing to look at video of a lap and make comments. Usually it works, occasionally it doesn't - I had one pro insist that I was taking a particular corner in too short a gear (I should roll through in 3rd rather than downshift to 2nd). I must have done a dozen laps in my next session, and it never felt right. My data showed that I was losing launch speed out of the corner every single time, and lost more time on the next straight than I gained. It was probably gearing/grip difference (I was in the 996 and he had been in a 2010 Cup, which has both slightly different gearing, as well as quite a bit more mechanical grip esp. in the back), but could have been me trying his gearing advice, on perhaps the wrong line.

[csmarx]

I also do a visualization exercise - think of a string tied between your toe and the steering wheel. When you're on full braking, string is all the way tight from the bottom of the wheel to your toe. As you turn, turning the wheel will lift your toe on the brake. As you press the accelerator after exit, think of it pulling the outside of the steering wheel back down, so that you have to accelerate.

I think that many novice and intermediate drivers are scared of getting too close to the trackout, as they're worried about getting onto (or over) the exit curbing. After all, their instructors have told them numerous times about bad things happening when they drop a wheel off the outside of a curb on exit. So in response they're staying away from track out, but their mechanism for doing so isn't doing a trackout to a lesser point, it's to keep full steering input in while exiting the corner, which at best delays their throttle input until they're pointed straight (killing their corner exit speed), or at worst adding throttle with full input, potentially causing spins or worse (exiting track when overcorrecting after attempting to catch a spin for example).

Jim

I've also used the "string theory" with students to good effect, but I quite like your phrasing of "releasing traction." It's a good image that gets the point across really well." I'll make sure to use that in the future!

As to your last point, I think most of us here on this forum are quite experienced and in some cases experts. So it's easy to forget that a novice often has no idea where his car is going to wind up on the exit of a turn. So it's no wonder they are nervous about going off the track and try to pinch it a bit. But I also think a lot of novices just go too fast for their skill because they are exited to go fast on a track.

I think the best advice an instructor ever gave me was that if you start making mistakes, just slow down to where you are making clean laps. Only then start to speed up - slowly. Repeat as necessary. By the end of the day you will be going much faster than if you just keep pushing and making mistakes. I still use that for my self.

-Christian

[TRAKCAR]

I think the best advice an instructor ever gave me was that if you start making mistakes, just slow down to where you are making clean laps. Only then start to speed up - slowly. Repeat as necessary. By the end of the day you will be going much faster than if you just keep pushing and making mistakes. I still use that for my self.



+1. So often I have to back up even an intermediate student. Somehow their previous instructors just let them go faster mistakes and all.

Different brake points, turn in, missing apexes, wrong gears prevents getting in a rythm and increases potential for spins or worse.

I make them back up to 7/10 (Their 7/10th) and tell them I want carbon copies of every lap after I take out their worst no-no's. I give them small adjustments that should not disturb the rythm. If they can do it, they already carry much more speed and lower laptimes then when they where going ragid 10/10th.

I am just after a rythm (Smaller mistakes and all), if they can do lap after lap without forgetting what to do you can go and continue to work on improving their driving.

[Gator Bite]

I think the best advice an instructor ever gave me was that if you start making mistakes, just slow down to where you are making clean laps. Only then start to speed up - slowly. Repeat as necessary. By the end of the day you will be going much faster than if you just keep pushing and making mistakes. I still use that for my self.

-Christian

I recently applied this at Watkins Glen. During my last visit there I had some pretty fast laps, but my consistency left something to be desired. This time I consciously broke earlier and found my consistency in the turns went way up. Then I could push a little deeper, a little faster per lap. My times were good. Not as good as last time, but more consistent. That's a win to me. With practice I should get the 1 or 2 seconds back and be consistent.

[Trackrat]

Not sure how I managed to not read this thread since it's inception. My loss, that's for sure. Pure gold. Thanks to all for the superb comments.

1. Balance
2. Sensitivity
3. Work up to the limits of the car incrementally
4. Comparing video and data with my track pals

Things that have come to mean a lot to me as I have pushed harder and gotten faster. I very rarely have an off (once a year on average) and very rarely scare myself while lap times decrease and are more consistent almost every single time I visit the same track. Must be some validity to that formula?

Braking technique in my world: no one size fits all, it is different for every corner for every track I run. But as a generality I have really been striving for a smoooooth release. For me, easing that transition from brake to throttle (even though the transition itself can be quickened or slowed, depending upon the situation) has meant a lot to my lap times.

Thanks to all for the fantastic food for thought!