Take a brake -- apart!

Hi all,

I hope everyone had a restfull holiday!

Boy, what a fun time, this front disc brake setup is (NOT!) After making myself a nice tool to remove the access cap, I discovered lots of crud and gunk inside the piston and caliper body.

I was able to get the outboard (left) piston out (with much cursing) :evil:

However, despite begging, pleading, screaming, WD-40, pounding with a big stick, and even lighting a few votive candles, I was not able to figure out how to remove the inboard (right) piston.

Question #1: OK, what's the secret :?: (I'm guessing it's a some type of compressed air trick).

Question #2: The one piston I got out has some corrosion around the lower circumference of the "skirt". I can remove most with a wire wheel, but some has eaten into the chrome plating. Is this still servicable, or should I get a new set of pistons and/or seals :?:

Question #3: When does one have to buy a new caliper body :?: :shock:

brake caliper

http://www.jerrydoe.com/forum/viewtopic ... 8&start=15

cut and paste from above link

Danger... never use pneumatics to disassemble stuck pistons, besides 125-150psi is nothing.

Reassemble caliper, and find adaptor and use a grease gun (1500-3000psi). to force piston out.
Work almost effortlessly on even the nastiest seize, at least it does for me!
Use a clamp to restrain the free piston.
HTH
Dave C.

added:
The grease gun I refer to, is the standard manual grease gun any normal car mechanic uses to grease their front end ball joints ect.
You will probably not need full pressure.

Dana,

I had the same problem - frozen inner brake piston. I didn't have access to a high pressure grease gun as per Dave's note so I got the bike shop to do it.

After getting it out I cleaned the caliper & inserted a new piston. The piston bore looked good (no crap or rust) but it got stuck as well. Maybe the guy in the bike shop stuffed up or it was bad to start with - I don't know.

I bought a reconditioned caliper at the local British Bike shop (at great expense).

I now have a disk brake that works but I wonder why I bothered. The braking performance is still marginal - I should have purchased a Lockheed or Grimeca caliper & adapter plate.

I am using a 13mm bore Master cylinder. It stops but you need to plan ahead.

Thanks guys,

D'uh ... now I remember reading that thread. Funny, it didn't ring a bell till I needed it.

New pistons cost $25 ea., if the caliper is not serviceable, it doesn't make sense to go after another stocker. If the caliper is OK, I'll get pistons.

I want to stop, not look pretty at the Concourse D'elegance :lol:

Lockheed Norton disc brake

I hear many complaints about this brake, but I know my '72 will lock up the front wheel long before I run out of strength.
Like many "improvements" to Commandos, you need to be sure that strengthening one part doesn't add more stress to the next weakest link.