All Mavericks and Comets utilize a dual hydraulic brake circuit in accordance with Federal safety regulations. Each circuit is independent of the other, incorporating a tandem master cylinder, a pressure differential warning valve, and, on disc brake models, a proportioning valve. One circuit services the front brakes (rear of master cylinder) and the other, the rear brakes (front of master cylinder). In case of a leak or other hydraulic failure, 1/2 braking efficiency will be maintained. A brake system failure will decentralize the pressure differential warning valve, actuating a warning light on the dash. A proportioning valve located between the rear brake system inlet and outlet ports in the pressure differential warning valve serves to regulate the rear brake hydraulic pressure on disc brake models to prevent premature rear wheel lockup during hard braking. I was going to post this in the Mystery wire / plug thread but didn't want to hijack it.....what this is saying is on my 1972 Grabber there is no proportioning valve, should I worry about this? will it cause premature rear wheel lockup during hard braking? I do have the rear disc set-up on mine, anybody else that has the rear disc set-up and no proportioning valve have any problems with rear wheel lockup during hard braking?
Disc/Disc...no proportioning valve here...my brake system Guy said if I was running larger tires on back than the front ,that is my bias...no problems so far...3 years...
Test it. In some deserted place, do a series of stops with increasing brake pedal pressure till you lock up all four. That will tell you if you have a problem. If you do, I guess an adjustable proportioning valve would be the fix.
All the expert opinions I've read say that a prop valve is only good for the system it was designed for, and that means everything from weight bias to tire size. Change anything and you might as well delete it...
I am glad you started this thread, because I will be swapping in rear disks and I have an upgraded new front disk setup already installed. This question has been on my mind the past few weeks. I was going to do the "take it somewhere safe and test it" method once I got it all back together.
Sounds good but is a out & out lie... Loose the rear and you may not even realize it till the first hard stop and it swaps ends with you... Loose the front and there may be 20% braking power remaining... Try to make a sudden stop and you'll slide into whatever just pulled out in front of you... I'll be using '69 Torino disc brakes on mine(installing today), with probably a Maverick disc M/C, not going to worry about a proportioning valve unless there is obvious issues with the system... If there are problems, I'll plumb in a adj aftermarket valve...
