Proper way to adjust proportioning valve?

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


  1. sunil6784

    sunil6784 Member

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    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?
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  2. Michael Yount

    Michael Yount Advanced Member

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    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.
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  3. sunil6784

    sunil6784 Member

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    Looks like I've got something to do today. :) Thanks for the help.
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  4. Michael Yount

    Michael Yount Advanced Member

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    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.
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