Manual Brake users??? Mr. Pozzi

[SHANE 73Z]

Hey all,

I just completed my home brewed brake upgrade and have little point of reference to judge whether I am satisfied with it.

Just for reference the car is a 1973 Z28 that is pretty close to stock weight. The only weight savings is an aluminum intake and some small odds & ends under the hood.

I had already completed th B-body spindle swap & 12" 1LE upgrade and was running aluminum 3rd gen drums. The car has 245/50/16 & 255/50 F&R Sumitomo HTRZ treadwear rating 160. With the above upgrades the car would not lock the brakes under any (dry) circumstances.

I have since added a Touring Classics C4 rear kit & I also upgraded the front calipers using SSBC Twin Piston (38mm) D52 replacement calipers.
This setup should have the same (basicly) fluid requirements as a C4 system.

I am using a CNC Brakes bias bar adjuster & manual dual 3/4" (spec'd by John @ JMC Motorsports) MCs with the stock pedal. I am very pleased with how the adjuster works, I have it dialed so that the car stops much flatter than before.

My question comes here, with the current arrangement the car still will not lock the brakes front or rear. The pedal effort is high (I wouldnt let a girl drive it!!!) but the modulation is fantastic.

What would going to larger or smaller MCs do to the effort & feel of this current setup?????

Thanks for your help,
Shane

[SHANE 73Z]

ttt

[fuzzyonion]

Smaller master cylinders would increase your line pressure, making the pedal effort easier.
The 3/4 masters would be about right for those calipers on a 1stgen car, but the 2ndgen has a lower pedal ratio. 11/16" would put you about right.

Smaller masters also increase pedal travel, but with dual masters, this isn't as much of a concern. You might even be able to go down to 5/8" masters and it would almost feel like power brakes.

[SHANE 73Z]

fuzzyonion,

That was my thinking. The beauty of the bias bar setup is now I can change masters realatively easy. There does seem to be some available 5/8" masters available with the common 1.4" stroke and I have pedal adjustment left if I need it. I am going to do some measuring to see what the manual pedal ratio is.

Thanks,
Shane

[fuzzyonion]

The spec on the 2ndgen manual pedal is 5.3:1
1stgen is 6.2:1

The 3/4" masters actually should have it real close to stock ratio in the front for manual brakes, just a couple points under it. With the big rotors, I would initially have thought that would be fine, but the rear discs add some increased pedal effort over drums, and since you say it is stiff.... an 11/16 would put it several points over the stock ratio.

I think a lot of people have luck just using hi-perf pads to make up the difference.

[SHANE 73Z]

Fuzzy,

I didnt realize there was that much difference in pedal ratio. I am going to give the guys at JMC a call and see what they think about it. I am figuring that they were used to dealing with 1st gen cars.

Thanks again,
Shane