Q: “I have been trying to improve my corner exit speed. As I am exiting certain turns, turn 1 at VIR for instance, I am at full throttle pretty much past the apex even before I fully straighten my steering wheel out. So, I am cornering at full throttle. Why am I not sliding or spinning? I am a firm believer in what you said many times in your books that the tires can only do 3 things at 100% – each either accelerate, decelerate or corner and they can do a combination of the above but only up to 100%. So, I am 100% accelerating and still cornering. How can that be? I drive a Cayman GT4 with Hoosier R7 tires. Can it be that these tires can handle more, meaning 100% full throttle in my car is really less than 100% throttle for these particular tires? I hope I am making sense!”
A: That’s actually a great question. The simple answer is your car does not have enough power to need all 100% of the tires’ traction for acceleration – it can’t use all 100%. That’s not to take anything away from your car because every car is like this, to some extent. So, there’s a point past the apex when you’re asking for 100% of your car’s acceleration power, but that might only be using 50% of the tires’ traction capability at that very moment. And at that moment, you must only be using 50% of the tires’s grip for cornering. It may seem that you’re still cornering hard, but you’ve either straightened the wheel enough to give some pure lateral grip back to the tires for acceleration… or you weren’t using all of the grip that the tires are capable of producing.
If you have a data system that can produce a g-g diagram (or gSum), you’ll see how this works in a more visual way. The classic Friction Circle is never a circle, because cars (with the exception of drag racers) don’t have enough power to keep the acceleration longitudinal g-loads high enough to make that part of the circle, a circle! The “circle” will have a relatively flatfish top.
As a driver, I’m always asking myself if I’m using all of the grip exiting a corner, trading off cornering by unwinding the wheel to give traction to the accelerating tires. It sounds like you’re doing that… what would happen if you got to full throttle a couple of car lengths earlier, when you had a little more steering still in the car?
Oh, and Turn 1 at VIR is an awesome place to work on this, as it has an expanding radius, making the trading off of cornering for acceleration a balancing act. I love it!
VIR Turn 1, for sure! Great test.