If you have been to a high performance driving school, recent motorcycle training or vehicle dynamics course at some point, the concept of the traction circle may be familiar to you. You weren't taught wrong. You just weren't taught right. For those of you who haven't been pulled "into the circle", here is a brief intro to the traction circle:
Your car (or motorcycle) tires want to give you 100% of their possible traction at all times. When accelerating in a straight line, the tires want to use their maximum grip to propel you forward. When braking, they want to use all their grip to get you slowed down. But when turning, part of their grip is being used for cornering. Maybe all their grip if you are cornering hard. And that means that you only have a fraction left for acceleration or braking (whichever you are doing at the time you are turning). When you make a picture of this, it can look like a circle where the edges represent your tires giving you 100% and anything inside indicates that you are using less than 100% of the possible grip. Up is usually accelerating. Down is braking. Side to side is turning. Something like this:
To make it practical, if you try to turn left hard and accelerate hard too, you're going to spin because you will exceed the maximum amount of gip of the tires - you'll be outside the circle.
So what's wrong with this info? I was just enlightened by a book - Ultimate Speed Secrets by Ross Bentley (I saw you roll your eyes that I'm trying to learn to drive fast from a book - hey, its on Kindle and I'm stuck at kid baseball games a lot lately!). Mr. Bentley has done some racing in his day and teaching - and is a keen observer of the technique of other which is a mighty valuable skill.
The issue is that at low speeds, cars have their max acceleration capability and they brake well too. But at high speeds, torque is far less apparent and braking is also less dramatic. If the torque curve were a diagonal line going ever higher with RPM and brakes could increase in size as you went faster...well then the circle would be perfectly adequate. But my car doesn't do that and I'd bet yours doesn't yet either.
At high speeds the top of the circle flattens out - and the sides push out a bit at the top too - less acceleration means greater cornering ability. This may seem like a minor, esoteric distinction. And you are probably right. But this is what created drivers like Senna, Prost, Andretti(s), Montoya, Vettel, Schumacher et cetera. They possessed the intrinsic knowledge of the fact that there is this "divergence in the force" as speed. They could attack the corners just that much faster since there is a bit more grip to be had at speed than you might otherwise think. And it becomes even more pronounced when you add in aerodynamic downforce....
So why bother learning about this stuff? The best I can come up with beyond my own geeky interest is the fact that it underscores what some of the autocross instructors have been drilling into our heads recently: stay in the throttle and you will make it through the turn. Lift and things won't get better. I can see now that they are hinting at the fact that you get a little more lateral grip ability from your tires when you (try to) accelerate at high speeds because you don't have much torque left to use up. Going up a gear is another way to reduce the torque that might otherwise rob you of grip. But you may have quite a bit of brake power still available...so hit those and you're going to spin. This knowledge may change your line on a high-speed track corner. It may also save your bacon in an evasive maneuver on the highway...
How would this change your line you might ask? According to Mr. Bentley, he watched the elder and younger Andretti apex much earlier than the competition at a less extreme steering angle - and then use the throttle to get the car the rest of the way around the turn. All at a higher cornering speed than the competition. Definitely a "speed secret" in there. And fascinating that most of these drivers figure this stuff out with their hands, feet, and rear ends instead of from a book while sitting on a bleacher watching kids bean each other with bats.
Well, now you've seen the "divergence in the force" as I have. Use it well. See you all on June 1 at Quonset Point.