How To Brake?

[beez]

Originally Posted by 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.

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.

[FTS]

Originally Posted by beez

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.

[beez]

Originally Posted by FTS

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.