Originally Posted by
SystemTheory
My simple question is this. In a turn of radius R and sweep angle A, you must cover a given distance S. Can you go faster along curve S while pulling fewer g's ? The skid pad helps you learn this lesson in the simplest study, that's all I meant to convey.
In some corners, yes you can. If you look at telemetry data from real race cars, they actually spend very little time at the maximum lateral acceleration. The tires can only have so much traction and some or most of it is either used for braking entering the corner or for acceleration off the corner. Typically you will see only a split second of max lateral acceleration right at the apex. Let's say that max acceleration is 1g. A good driver (let's say it's Schumacher because I have seen his data in a magazine before and he really is a master) will stand on the brakes near the end of the straight using all his traction for braking. As he begins to turn into the corner he will ease off the brake to have the traction needed for cornering but does NOT jump all the way off the brakes. He gradually releases the brakes while gradually increasing steering input so that linear acceleration reduces while lateral acceleration increases. He wont hit that full 1g lateral until right at the apex as he finally comes all the way off of the brake. This last for a tiny fraction of a second as he then starts to reduce steering input and adding throttle. Now as the lateral acceleration drops, the linear acceleration increases.
So what does this mean for achieving max g's? Well, let's say this car Herr Schumacher has been driving is really well balanced and he is very happy with the car. Now some engineer comes along and says "this spring rate will improve grip." So they make a change and go out again. This time the max lateral g seen for that split second in the middle of a corner is 1.1g. This is better right? Except the laptimes are slower and Schumacher is griping that the car is junk. How can this be?
Well, we did increase grip but in the process we made the car very unstable under braking so he can't go into the corner as hard. The extra lateral grip allowed him to let off the brake sooner, thus increasing the max g number at apex but having to brake so much sooner and so much more carefully has hurt the straightaway speed and laptimes.
Or, maybe this gave the car a bad throttle push exiting the corner. He wasn't able to stand on the gas as hard on exit and therefore straightaway speed suffered.
Of course, now that we know the car is capable of more grip, perhaps we can play with some other things to improve the transitions while maintaining that grip.
My point is, skid pad data MAY provide some useful data but you can NOT set up a car on skid pad data alone and expect good results. For instance, take a car with a 500lbs, 500 hp engine and run it on a skid pad. Now replace the motor with a 400 lbs, 200 hp engine. The reduced weight is going to improve the skid pad numbers but laptimes will be much slower on a real racetrack.
One RC class where I could see skid pad testing being useful is spec rubber tire stock TC's. Their low power means they spend more time at a more or less steady state, grip can often be hard to find and you don't have the option of slapping a softer set of tires on it. If you could find some grip on the skid pad without having to resort to any unpractical set-ups you just might find some laptime improvement.