Proportioning valves are recommended to be installed in the rear brake circuit. The point being that you always want more brake bias in the front brakes - a ratio of about 2 to 1. In a recent post two people mentioned they installed it in the front brake circuit. Their point being with “skinnies” on the front and slicks on the rear they want to decrease front braking. This makes no sense to me since the skinny fronts would have way less grip than the rear.

It would seem to me that if you have to decrease front braking, you don’t have big enough brakes on the rear.

One person commented that “if you chose the right m/c you don’t have to worry about a prop valve”. The fact is: m/c size doesn’t play into this. The m/c will only change the pedal travel and the foot pressure required - the volume of fluid required and sent to the brakes remains the same. Changing m/c’s doesn’t alter the bias.

So can someone please a plain the reason or logic to putting the prop valve in the front brake circuit.

Well, i don't run one. Just a standard, aluminum Omni ( if i remember, been 27 years) since i put it in. I do remember putting in a new one a few years back). If they have built in bias, mine is hooked up backwards to boot . Works great, at 158 mph, no problem! When you consider the difference in braking capacity differance between a 25x3.5 tire up front and a 33x 15 in back, plus rhe rears are a race compound, it all worked out perfectly for my Dart, even if by accident

Some of the old ,pre 1990 when I quit racing NHRA stock classes racers, like holding the brake pedal and gas peddle to control their burnouts so they hook the line locks to the rear brakes to the block off pressure to them during the burn outs

I ASSume we are talking discs all around, this is the race section after all. If so NO prop valve is needed, the piston size, just as in drums with a cylinder will "self regulate". Do yourself a favor and buy a brake pressure gauge and learn about the relationship of pedal ratio and pressure. If you simply want to be able to adjust the amount of fluid moved between the front and rear then by all means ad a prop valve. But it is not a REQUIREMENT for a 4 wheel disc set up.

FWIW I have NEVER run one with a 4 wheel disc set and never had an issue. This includes cars I have built for myself and other to include cars with carbon and carbon/steel rotors. I've owned two ex pro stockers and they do not use one. All my cars we use a brake pressure gage to set them up and with pedal pivot/arm relationships and m/c bore size to achieve the correct pressure its never been an issue.

If you have front disc and rear drums then yes you will need a prop valve. The reasoning is the area of the wheel cylinder and disc piston being different.

I am primarily concerned with a disk/drum setup. But did want to hear what others have to say.

I noticed in the other post about someone using one on the fronts and thought it was a little weird...

Then I think back to last summer when I put a few passes on the Dart on a less than ideal road and understand why they do it...

Under hard braking you can hear the fronts trying to squeal and have to let off the brake a little...

Had I had a valve on the front I could have used more brake and not had a problem...

FWIW mine is just standard 73 A Body spindles up front with 3.5" skinnies...

While the rear is the typical 10" x 2.5" rear drums...

Mines slow and only runs about 110 mph...at speeds earlier discussed I would add a prop valve to the front of mine...