disc brake master cyl.

[BROWN 70]

hi, I bought a new mc for my GMC, on it was the large reservior in the front and small in the back. I was sent the two equal size resevior. I understand one is Bendix and the other Delco moraine. do these interchange? 71-72 disc brakes. thanks, BROWN 70

[Steeveedee]

I see that no answer has been given. I bought a new master cylinder and had the same experience. It's working fine, so I have to say that they interchange. Braking performance doesn't appear to have changed at all...except that this one doesn't leak. I updated to disc brakes about 10 years ago.

[BROWN 70]

thanks so much steeveedee, I don't ask a lot of questions on this forum but I was surprised know one replied. your info is just what I needed. I was getting ready to rebuild the old one. thanks again, BROWN 70

[Steeveedee]

Originally Posted by BROWN 70

thanks so much steeveedee, I don't ask a lot of questions on this forum but I was surprised know one replied. your info is just what I needed. I was getting ready to rebuild the old one. thanks again, BROWN 70

You are quite welcome. The metals I see these days on most any brake component, I just replace them. Didn't used to be that way. I've rebuilt hundreds of MC and WC back in the day. I only wasted my time once on some 4-piston calipers that were used in the late '60s. There always pretty much junk, and just needed to be replaced. Best thing GM did was go to a stainless steel piston.

[Rust_never_sleeps]

IIRC, the cavities in the MC are different depths, so you may have to adjust/switch pins to match
This is what I have in my notes:

Master Cylinder:
shallow is 1/4" Moraine style
deep is 1 5/8" Bendix style

[PbFut]

Just a little extra info. The size of the reservoir will not change the braking characteristics in any way. It is the piston size in the master cylinder relitive to the piston size in the caliper that will change how the brakes act. Each cup feeds to each circuit. So if a line fails and drains the one cup, the other circuit, front or rear, still functions. The idea for different sized cup is to maximize efficiency for each circuit. If one circuit is using different sized master and slave pistons or has different wear rates on the pads. You will need different reserve requirments of fluid to take up the space made in the caliper cylinder as the piston drops to take up pad or shoe resting position. Typically, front pads wear faster than rear shoes. So there is a greater need for more fluid to take up the space in the front calipers as they drop in the cylinder. The rear shoes have a mechanical method make up the space so no need for large reservoir only enough to take up the space between mechanical clicks on the adjuster. This is why you should do a hard brake while in reverse from time to time. The action in the shoe assembly will cause the mechanism to ratchet the mechanical adjuster.

[70STOVEBOLT]

[QUOTE=PbFut;9375004 This is why you should do a hard brake while in reverse from time to time. The action in the shoe assembly will cause the mechanism to ratchet the mechanical adjuster.[/QUOTE]

I believe this is only true if your truck is equipped with self adjusters.

[BROWN 70]

thanks to all the members for your replys. BROWN 70