DeTomaso Mailing List: December 99, Message #135

     Dan, Mike D,
     
     A car with 40% of it's weight on it's front wheels can get maximum 40% 
     of it's brake force from them in a static scenario. Moving, with the 
     associated weight transfer, this will change. The Pantera has in the 
     10-20% range of weight transfer with it's low center of gravity. 
     Drew's claim of 90% is for a motorcycle, you can do stoppies on a bike 
     but not in a car, and not something that a street car will ever see.
     
     As the ideal setup for optimum braking requires all wheels to lock at 
     the same time, you always limit the end of the car that locks up 
     first. Now in the real world you have to dial out a little more rear 
     than optimum as you have the engine contributing to a degree and you 
     normally deliberately set the car to lock the fronts first.
     
     The stock early Pantera calipers give you around 65% front and 35% 
     rear brake bias. By limiting front circuit pressure by almost 50% 
     you'd get a good brake balance. A friend on the list tested his 
     otherwise stock system with a Wilwood limiter in the front circuit 
     this Fall and reports that the fronts lock first even with maximum 
     pressure reduction. The Wilwood reduces output pressure to 67% of 
     input when set to max reduction, and even that is not enough 
     adjustment range for the Pantera as you see.
     
     Plug the rear circuit and front circuit one at a time and see what 
     kind of Gs on a meter you can pull with only one circiut operating at 
     a time. I predict more Gs with the rears alone than with the fronts 
     alone.
     
     Tomas


______________________________ Reply Separator _________________________________
Subject: RE: Re[2]: Suggestions on brakes???
Author:  "Jones; Daniel C" <Daniel.Jones@MW.Boeing.com> at Internet-europe
Date:    1999-12-08 15:30


You'll have to explain why that is so.  Under braking, the majority 
of deceleration comes from the front brakes.  When the limiter kicks 
in, my rears lock momentarily, increasing braking distance.  All of
the other cars that I've driven have proportioning valves which reduce 
pressure to the rear brakes after a certain pressure is reached.
     
Dan Jones
     
> If the pop-off valve you refer to is the front circuit pressure 
> limiter I can tell you that removing a functional limiter from a stock 
> system is a sure way of increasing, not improving, the brake distance. 
>      
> Tomas
>