67 evil eleanor

You need to think in terms of percentage of brake, not pressure. Say 70/30 front to rear and read the attacked article on "how" the valve works. It may very well be working right and your not giving it enough time for the pressure balance to occur and the rear to lock up. A "stab" will usually lock up the front up first. Changing the surface area of the pistons will require a re-balance of the braking system. Another consideration is the "line loc". I'm not sure that this may cause a delay in the fluid travel (slower movment of the front brake piston) and cause a little problem. ALso leaks, trapped air and expanding brake hoses can cause frustrations.

"If equal braking force were applied at all four wheels during a stop, the rear wheels would lock up before the front wheels. The proportioning valve only lets a certain portion of the pressure through to the rear wheels so that the front wheels apply more braking force. If the proportioning valve were set to 70 percent and the brake pressure were 1,000 pounds per square inch (psi) for the front brakes, the rear brakes would get 700 psi."

lilrobo

sixt5 dad here,, when we installed the system we adjusted it every way we could and no lock up ,, we would like to see the rear lock up and then we could adjust the valve ,, so far nothing , i think with the larger calibers in the front it need more fluid ,, dont know ,, even after we bleed the brakes and the lines are full of fluid and when applying the brakes there is not enough fluid going there to fully lock up ?????but one the other hand shouldn't the back lock up if adjusted right cause they are getting the right amount being stock cylinders ??? again we dont know

thanks

Starfury

Even if the m/c is the problem, you'd need a m/c with a smaller bore, not larger. You have to think about it in terms of pressure, not flow. The braking system requires minimal flow, and unless your pedal is dropping almost to the floor, flow isn't the issue. Pressure is. Pressure is a function of bore size, and the smaller the m/c bore, the more pressure you're going to have in the system.

I still think you need to adjust the rear brakes out. You should hear the shoes barely rub the drums when turning the wheel off the ground.

If you adjust the brakes out and still have the same problem, bypass the line lock and see what happens.

lilrobo

what would you say has the smaller bore master cylinder ,power brakes disc or shoes ?? ,, cause we have disc in front and shoes in rear