REBUILDING BRAKE CALIPERS - ??? help please

[SloKrt]

Im about to tear into my forks in the next couple weeks. I am going to replace the fork seals, but while it have everything apart i want to take care of everything else while im there. Ill be painting the forks, painting the front rim (rear later) replacing wheel bearings, brake lines, speedo cable. Painting the center section of my disk and possibly having the disk resurffaced and getting some new brake pads too.

On to my question.... since im doing all of this i figured i would also re-build my caliper (or do i need to).

Is this a must do? I plan to paint the capiper too, so if i need to or should re-build the caliper, i figure now is the time.

My question is... Do i need to re-build or not? front brakes worked, though not great (might have had some fork oil leaking on them) before i started taking the bike apart. how do i know if i need to re-build? What do i need to do? and what is involved? I am prety handy with a wrench on cars and trucks, but havent done bikes before, what should i know or be looking out for when i dive into this? or do i event need to???

Help Please!

 

[hillsy]

When was the last time you fully drained / changed the brake fluid? Have you ever done it?

If you don't know the answer to the first and answer no to the second then there's bound to be a ton of sludge inside your caliper that needs to come out.

Pop out the piston and inspect / clean / replace as necessary. If the piston is not scored or corroded and the caliper wasn't leaking you should be able to re-assemble it without the need for new seals.

 

[SloKrt]

Thanks for the tip!

Well since I recently purchased my XS I'll assume that a flush and clean has never been done. That said ill start there. How do I know if the seals are bad and needed to be replaced? It doesn't appear to be leaking now. Any pit falls I should watch out for?

 

[620dark]

With something like brakes, if you are saying to yourself "I'm not sure if the seals are good," they are probably not good.

At the very least you should tear down the caliper like hillsy said and see what things look like inside. Your piston may be a mess, your caliper body may be filled with something that looks like boogers in Vaseline, and your seals may be torn up and sad. Your dust boot is probably pretty messed up just because of age, and once that goes, the seal/gasket on the piston can get torn up by crap getting past the boot.

Also, if you tear it down, you can really go to town cleaning and prepping it for paint. If fork oil has been leaking on your caliper, your pads may be compromised as well. Oil + brake pads = sadness.

To get the piston(s) out of the caliper, you can use an air compressor to shoot air through the brake hose fitting on the caliper. Make sure you have a bunch of rags or a piece of wood in place to catch the piston, however, as I almost took out my Dad with a stuck piston that became unstuck. It took us 20 minutes to find it in the back of the barn it flew so far.

 

[hillsy]

A seal is a seal. If it leaks, it's bad. If it doesn't, it's good.


If there is corrosion on the piston it will more than likely fubar the seal on it's way out of the caliper.


You can re-dress the pistons to some degree with wet and dry (always sand AROUND the piston, not up and down). When I was in the shop we used to spin them up in the lathe and dress them with wet and dry.


If there is pitting in the seal area they are beyond repair and will need replacing.

 

[DreadRock]

And if your going to be re-building them dont for get to use something like Permatex ultra Disc brake caliper lube Item # 24110 will make thing easier .

 

[620dark]

I've had bad luck with seals that look good, but then again where I live everything metal turns to dust and everything rubber turns to either a hard cracked plastic or a black goo after a decade or so. I guess my point was that if there is any question about how good a seal is, it's best to err on the safe side.

 

[jay_kent]

for the cost of the seal, just replace it. skimp on the paint. You need these to work.

+1 on using compressed air to eject the piston. Works a charm.

 

[SloKrt]

Thanks for the info guys!

Since I'll be taking them apart to clean em up. I'll spend the few extra bucks to have piece of mind on the road later. Oh, and thanks for the permatex tip... I'll deff pick some up for reassembly.