Big Brake question

[timkins]

I installed a Big Brake Kit on my Mustang II equipped 32. It has 11" Grenada rotors with GM calipers (Mid 80's). I am not real happy with the way it stops so I called "Stainless Steel Brakes" and asked if their "Quick Change Aluminum Caliper Upgrade Kit" which is supposed to be a "direct bolt-on replacement for the heavy stock cast iron calipers" would work. They said "no" it would not work because it did not have GM rotors on it. What is the difference and why wont it interchange?

[enjenjo]

The thickness of the rotors. GM rotors are thicker than Ford rotors.

[timkins]

If it is the thickness of the rotors, I should be able to use the SSBC calipers and just keep an eye on the distance the cylinders come out or the thickness of the brake pads and adjust accordingly. Correct

[enjenjo]

There is considerable difference in the rotors, on the order of .250 or more. There also may be a difference is diamter, not sure on this, but I recall turning a Ford rotor down to work on a GM spindle one time.

[enjenjo]

After reading your first post again, I believe you have other problems. The caliper and rotor you have should give you great brakes. If you don't have great brakes, I believe the problem lies elsewhere, and changing to a bigger caliper won't fix it.

what do you have for a booster? what master cylinder? whats the pedal ratio? And what exactly is the problem? Not great brakes is a bit vague, it just won't stop? excessive pressure needed on the pedal? Give me some more details.

[timkins]

No booster. Not sure of the master cylinder. The pedal ratio is 6.5-1. I just did not notice a great deal of difference when I changed from the 9" originals to the 11" big brakes. Hard pedal but did not stop any easier or quicker. If I really jump hard on them I can lock the rear brakes up but not the front. I have an adjustable proportioning valve on the rear with a 2# and 10# residual valves. A suggestion I got on another site said to get rid of the P-valve and go with a combination valve which is where I think I am heading over the winter.

[enjenjo]

well, the equipment you have should work good if it's set up right. I'm guessing you have a "Corvette" master cylinder. See If you can find a casting number on it. My guess is there is a mismatch between the master cylinder bore and the caliper bore.

If you can lock up the rears, but not the fronts, you need the proportioning valve, and it needs to be backed off a bit.