Proportioning valve/Roll Control

[mrtimstik]

I have a few questions about the braking system on my car at the track. What is the correct reason for having a brake proportioning valve on the car? At the track, do I(Number 1)crank the rears closed(no fluid pressure to these), do my smoky burn-out and then my run? This concerns me because I will only have front brakes at the end of the track when I believe stopping is far more important then going. Or, do I(Number 2) adjust this valve to allow the front disc brakes to have slightly more grab than the backs(a how-to needed here) and use a button activated, "Roll Control" to lock my fronts for the burn-out and maybe launch? I am confused and welcome any comment that will help me have fun with my car. Thank you very much folks. Tom

[Seattle Sam]

Hi Tom,
I definitely would not disable the rear brakes by adjusting the proportioning valve. A line lock (roll control) is the way to go with a stick car to help with burnouts and staging.

Before adjusting the proportioning valve, I would first make sure all your individual brakes are adjusted properly. Lift each wheel off the ground to check. Your front disks should offer a little drag as you spin each wheel, and you can adjust the rears until you feel drag then back them off a little (If you have limited slip you need to get both rear wheels up at the same time).

If you have a standard brake set-up (factory size brakes front and rear) you might want to use the standard factory proportioning valve that will not require any adjustment. If you have beefed up your brakes and need an adjustable valve, call the manufacturer and ask them what setting they recommend to start with.

Then I would find a safe, open, low traffic area for testing (maybe a big parking lot after hours?). Speed up to around 20 MPH and stop real hard, to the point of lockup. If the fronts or rears are locking up first, then make an adjustment to the proportioning valve. If one wheel locks up, check out the brake adjustment on that wheel instead. If they seem to lock up all at once, then you are done.