Proper way to adjust proportioning valve?

Discussion in 'Fox 5.0 Mustang Tech' started by sunil6784, Mar 11, 2006.

  1. Had the top down for the first time this year yesterday. :D I got out of my car and I was looking at the wheels. The rear wheels had a lot of brake dust on them, whereas the fronts had hardly any. Also, the car feels like its got too much bias for the back wheels. I want to adjust my proportioning valve, the car has a turbo coupe rear end in it, w/ 3.55's and 4 wheel disc. What is the proper way to do this? Also, on the proportioning valve, there is an "increase," and a "decrease." Does "decrease" mean "decrease" rear bias?
  2. The best way to adjust it is to obtain the help of another person and head to a deserted good sized parking lot. Fuel load should be about 1/2 tank. Have the other person watch from outside the car -- both sides -- while you make stops from 45-50 mph braking hard enough to lock the tires. Your 'spectator' will tell you which end is locking up. Keep adjusting the proportioning valve until the front brakes lock just a hair before the rear brakes do. The front brakes do MUCH more of the stopping in a car like the Stang when the proportioning valve is adjusted properly. You don't want the rears locking first for 2 reasons -- 1) when the rears lock first you're not getting maximum stopping power out of the fronts, and 2) the rear end tends to come around.
  3. Looks like I've got something to do today. :) Thanks for the help.
  4. Yup - you really can't do it correctly by yourself. The beauty of ABS -- it takes care of proportioning on a wheel by wheel, stop by stop basis.