Cleaning up caliper bores

[Dogma]

I've cleaned and rebuilt about 15 calipers in the last 5 years.Of those 6 had pitted, rusted or cracked/missing chroming on the pistons. Each of those 6 calipers also had concretions on the sides of the bores hard enough to require scraping. On the advice of my pro-wrench I used the dremel brush technique to clean them up.

I think, like plaque in a human artery, if any of that crud breaks off or remains in the bore it stands a good chance of plugging the "in" line or working its way passed the seal or possibly damaging it. The chances might be slim of this happening but I'm not keen on a possible problem so I'd rather clean it up when I find it.

Out of habit now I routinely dissassemble, clean and rebuild the calipers on any new to me bike and I'm doing that this weekend on the 550. I'm convinced that folks generally don't give a moments thought about their brakes unless there is an obvious issue. You can tell right away how well they've been looked afterwith a quick peek at the colour of the fluid. Everyone I've looked at has been brown to black. Call me paranoid, but an ounce of prevention is always better than a pound of cure.

Ride safely friends.
spyug

+ 1 gazillion to all of that.

Oh, and the wire wheel won't hurt anything unless you get stupid with it. I find that the steel ones last a lot longer than the brass before coming apart. Furthermore, the only part of the caliper that actually matters to sealing is the OD of the seal groove. Even that can have small pits and still seal. It just can't have a pit large enough to cross the sealing face. The walls (and pits on the OD) only need to be free of burrs that could cut the seal.

[seano]

Thanks again for the wealth of information as I like to only do things once - ok, maybe only twice . . .

[seano]

The vinegar did the trick very nicely. Thanks Chuck!!

[spyug]

I pulled my front clipers from the 550 yesterday broke them down. The left one was clean but the right one looked like this:


Lots of crud built up at the bottom of the bore, almost like a mud. Thankfully soft and easy to remove:



The seal was good but there was crud behind it which had pushed it outward slightly and caused it to jamb the piston. The piston was easily removed with a shot of 80psi compressed air through the transfer port ( the little hole in the casting) and it had no pits or cracks in the chrome. For any newbs attempting that procedure, wrap the piston/caliper with a good rag and hold it down firmly on a bench with your hand over the piston. It will come out with some "violence" and if not contained the piston could become a deadly projectile. Keep your face out of the way.

So now having looked at 17 calipers I can add another one with issues and I still need to look at the back one.

I'm putting the calipers back on today in hopes of road testing the bike later or sometime this weekend.

Cheers,
spyug

[JimmyR]

Yeah I'm rather fussy about brakes too. I will never understand how some guys spend so long refining an engine to produce more power and not pay so much attention to the brakes. I've only ever worked on two bikes but on both the first thing I did was maximise the brakes' abilities to stop the bike.

[spyug]

Well I tore into the back caliper this morning and it was the worst of the three. One side was gummed up around the seal so the piston didn't move. There was considerably more gunk in it to and both pistons were on there way to pitting close to the mouth but above the seal so still useable. By the looks of the pads which were unworn, the brake was never used. So I get to add that one to my list of dodgy ones, so the score is near to 50/50 at this point.

With odds like that, I really can't understand why folks don't pay more attention to them. If that bike had been ridden with one non functioning back brake and one oil soaked front it would have had the stopping power of a bulk oil tanker.

There are things you can fool with but brakes, tires and wheel bearings are things you can't. If you can't work on them yourself, for goodness sake get a pro to take a peek.

Ride safely friends.
Spyug