Reply to "Brake Upgrade: Done, but Bugs to Work Out"

Considering all the work that was done and the diagnostics, I have to agree with Chris and say that the front needs a proportioning valve in addition to the rear.

There is too much pressure going to the fronts. They now have too much bite.

You have to reduce the pressure to them until you can no longer lock them up, or just barely.

You can only do that with an adjustable proportioning valve between them and the master.

Your setup is just going to have a proportioning valve to the front and to the rear.

I don't know why it really should need one but it will give you the ability to completely re-balance the system to your liking.

You have to go with what Chris recommends on this. He is the only one that has done extensive modifications to the Pantera brakes AND is participating in this discussion.

What you are experiencing as far as the front left/right balance issue is possibly what the DT factory experienced in testing the car and the reason they put the balance valve in the plumbing to begin with?

If the front imbalance continues even after you install a proportioning valve, the only logical thing to do after that would be to put it back in the system.

As an added note, the ONLY "production" car I have ever seen that it seemed impossible to lock up the brakes on under any circumstances was the '65 and '66 Shelby GT350.

They added an adjustable Bendix unit to the rear brake line, before the rears.

It actually was one from a Corvette. Don't know what model year, but Bendix gave Shelby their own part number on it.

You could accurately describe this brake system as a mechanical ABS brake system.

Having driven those cars I can tell you that it is virtually impossible to lock up the brakes either in the front or the rear even if you stand on the pedal.

The reason I mention this is it makes precedent in adjusting or designing the brakes in this manor in case someone said, "no, they aren't working right unless you can lock the fronts up".

This post should also stand as a WARNING to the issues ANYONE is going to experience in UPGRADING the brakes on this car. There IS some re-engineering of the system to do and it isn't child's play.


I don't remember what you said about the master cylinder, whether or not you replaced it.

Some masters come with a little rubber check valve that is intended for use with drum brakes. The drum brakes need to be kept on the verge of dragging all of the time and the check valve keeps the fluid from draining back to the master.

The same masters are often used with the disc brakes but you take that valve out of the line to use them with discs since you want the pistons to back off some when you release the pedal.

Your fronts are showing some of those symptoms as well as a sticking piston to one side.