V1.2 Nov 22 2006
This is a work in progress, and it has been a very long time coming. I intend on working on it for the next little while, dumping as much of my brain and hard-earned knowledge into the public record. It is, however, NOT public domain; I reserve the copyright for myself. You may NOT duplicate this elsewhere without my express permission - and this is the age of Google, folks, I WILL find you if you post it elsewhere. Otherwise, read and enjoy, and put this all to good use. Go fast!. DG
I had the good fortune to fly to Germany on a business trip, seated next to a Chrysler brake engineer. This engineer had with him a plot of braking force vs pedal force for a number of Chrysler cars.
Every graph had a similar shape: a line that rose sharply with increasing pedal force, followed by a little dropoff, followed by a flat line. It was explained to me that the dropoff and flat line in braking force was the ABS engaging - once the ABS is on, braking rate is flat no matter how hard you push on the pedal.
But it was that little bump that was interesting. That bump indicates the area where a human can outbrake the ABS. If the driver is properly threshold braking, he can stop faster than if the ABS is active.
And as you make the car lighter, the brake pads grippier, and the tires stickier, that little bump on the graph gets bigger, as the ABS has no way of knowing that the tires are now 40% stickier than the tires the ABS system was designed to.
My own testing proved it. On concrete, with race tires on, I could consistantly outbreak the ABS system.
So anybody whose plan is to stand on the brakes and let the ABS do the work is giving up time.
The opposite is true in the wet; the max grip level has dropped to something more like the ABS's braking limit, and the ABS unit will beat the driver.
Overall, I'm a fan of ABS in race cars. In the dry, you treat ABS activation as locking a wheel and you back off and remodulate. In the wet, the ABS keeps you under control.
But best of all, ABS keeps your nice expensive race tires round - no flatspots.
The typical ABS system doesn't weigh that much and pays for itself the first time you prevent a flat spot. Put it on the car.