Proper way to adjust proportioning valve?

[sunil6784]

Had the top down for the first time this year yesterday. 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?

 

[Michael Yount]

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.

 

[sunil6784]

Looks like I've got something to do today. Thanks for the help.

 

[Michael Yount]

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.