How To Brake?

[NickW]

Originally Posted by bman

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.

Originally Posted by bman

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).

Originally Posted by bman

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



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

Originally Posted by NickW

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]

Originally Posted by bman

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]

Originally Posted by bman

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

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]

Originally Posted by NickW

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.

[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!

[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]

Originally Posted by FTS

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!

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

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

[FTS]

Originally Posted by bman

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

I never kid about VIR, and no doubt I have a (or more) problem(s)

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

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.