rear brakes lock up

[DREW78BU]

I just installed a ford 9in in my malibu and I put the QP rear disc brakes on it. I ordered a proportioning valve from pirate jacks for the disc/disc conversion. I just test drove my car and for normal stopping it seems to work fine. If you were to panic stop then the rear brakes lock up. I have heard not to use the adjustable proportioning valve. So whats next??[/img]

 

[John N]

I think an adjustable prop valve would be secondary tuning device and only cut pressure to the rear calipers which would help ???

 

[LS6 Tommy]

Did you get a Combo valve, or just a proportioning valve? Either way, the adjustable prop valve will need to be closed till the rears don't lock so soon.
A good starting point is to put the car up on stands. Have someone turn the front wheels as you slowly apply the brakes. As soon as the fronts are locked, hold that pedal pressure and have them try to turn the rear wheels. Keep adjusting the valve closed until the rear wheels still barely turn. Once you get the valve adjusted to this point, drive the car on gravel or something similar at a low speed and make your final adjustments.

Tommy

 

[DREW78BU]

I got the combo valve. I do have an adjustable but i haven't put it on yet. thanks for the advise.