Drag car brake/proportioning question
Thanks for all the thoughtful replies guys!
So if I go with a proportioning valve can I eliminate that residual valve or should I run both? Is this type ok? That way it could mount under the car with the MC and the adjustment could be in the cab.
View attachment 1715508864
View attachment 1715508865
Why in the hell is the master cylinder under there? There's no way I'd leave it there. With a rubber flap around the hole in the floor? Geez.
If you did leave it there, yes, you might need to retain a 2psi residual valve because the master is going to be lower than the calipers are. Residual valves are commonly either 2 psi for disks or 10 psi for drums. But yeah, I don't like the looks of that set up at all.
The adjustable proportioning valve can be run on the rear line under the floor with the adjuster in the cabin if you really need it to be. Unless you're constantly changing your weight balance, suspension settings or tire compounds that's not really necessary, you can set it and then leave it. If you are constantly changing those things then remember to be really dialed in you'd need to test and adjust the brakes every time you changed any of that stuff.
As Andy said, if you have a brake system designed for your car then you may not need one. But aftermarket brakes are generally adapted for use on different platforms, so, just because you have a kit that fits your car doesn't mean it was designed for it. So the adjuster allows you to dial in that balance if you need to. It can only reduce pressure to the rear brakes though. And if it turns out that you don't need it because by some stroke of luck your brakes are perfectly matched to your car set up, you can just leave it wide open.