Front Caliper Rebuild question

[Bruno]

Hi All,

I'm rebuilding the calipers on my bike. I'd like to replace the boots all the way around. The rear set are no problem. Maybe I'm missing something here, but I'm not seeing how the front set come out. They appear to be pinched in the cylinder somehow. They are actually in pretty good shape for being 26 years old. Should I just leave them alone and just change the seals?

You can kind of see what I'm talking about in the picture below. The boot is pinched between the outer housing (which you can't see because it's under the boot) and the first rusty ring. The only way I can see to get it out is to rip it, but then I don't see how I would install a new one.

Also, for those of you who wish to see my GS850 project, I just posted some pics in the Appearance Mods forum.

[Steve]

The boots should just lift off. Pry the seals out with a small pick. Best to replace them while you have them out. Clean the bore and the piston with a ScotchBrite pad (a worn-out one from the kitchen works well) before re-assembling everything.


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[Nessism]

What Steve said...

The brown stuff is solidified frame fluid, mixed with rust. They typically say to not use solvents on brake parts but I used a little brake cleaner to spritz out the crap in one caliper I have.

When putting everything back together don't forget to put a little silicone grease on the sliding parts. Makes a big difference.

[Bruno]

Thanks! So apparently, the boots are just so stuck that it appears that they were pinched in there during the manufacturing process. Just wanted to be absolutely sure before I ripped 'em out. I'm guessing I'll then be able to clean out the groove they sit in and the new boots I've ordered will just pop right in???

The only reason I asked at all is that these boots are in there TIGHT! I've tried pulling on them with significant pressure to see if they will start to split away from the housing and they don't move. I think the rubber will tear before they leave the groove they sit in. It's like they are stamped in under a ring (although I know from the parts diagram that there is no ring).

[mortation]

The boots are just stuck in the groove. Pull em out. Clean them spotless with brake fluid.

[matt_gs450]

Hi Bruno,

Take a quick look at my rebuild:

http://www.stupidcatchphrase.com/moto/gs450t/front-brake-rebuild/index.html

I'm interested, once you get the seals out and the caliper cleaned, if you see the same sort of pitting that I did in the seal groove. My brakes have been working fine now for a couple months...

[Bruno]

Thank Matt. That shows me just what I needed to see. That channel is really thin. I can see why those boots are stuck now. I should just be able to clean it well and the other boots will pop right in.

I'll let you know about the pitting. I'll check this weekend.

[BentRod]

first time i rebuilt a from brake caliper... I ended up using a beer bottle cap for 75% of the work.... they are soft so they didn't etch or scratch...

[txironhead]

first time i rebuilt a from brake caliper... I ended up using a beer bottle cap for 75% of the work.... they are soft so they didn't etch or scratch...

Plus drinking the beer that was under the cap makes the work go by easier.....

Those seals can be stuck in there tighter that you'd believe. It's a combination of road gunk, leaking brake fluid, fork oil, 25 year old rubber, and probably some bug guts thrown in.

Mine looked much like that and I ended up stripping the paint off, cleaning everything inside and out (used several brass brushes, some scotchbrite pads and my dremel) and then masked and repainted them. They look brand new now.

[Bruno]

Thanks for the tool tip, Bent Rod. I'll try that.

txironhead, sounds like we have the same bike. My front calipers were disgusting. Nastiest thing on the bike. Nice to know you had the same experience and everything turned out ok.