Rebuilding Front Brake Calipers

[Hegemon]

I have a brake caliper to rebuild, it's quite froze up (piston stuck)

Does anyone have a tip on how to free things up for the rebuild?  I do have compressed air for the "finishing touch" if needed, and no I won't forget to duck <grin>

My current project is a 82/83 hybrid, now running prety well, excepting the typical charging system problems, however I have a handle on that part.

Thanks all

[Lucky]

sometime you simply can't free them up..  i'd first try soaking it in a big container full of brake fluid (seal it well) overnight.  then, stuff a rag infront of the piston & hit it with shop air (9o lbs should do it) you may need to tap on the caliper to set up a little vibration while hitting it with the air. if that doesn't get it out, i doubt anything will...

watch your face when the piston comes out!!
--Lucky

[Hegemon]

Thanks Lucky,

I thought that might be the case, and yes I will keep my face out of the way.  Not that an impact mark on the forehead wouldn't be an improvement.

I'll post along as it goes, thanks again.

In the worst case, does anyone have a line on a right side front brake caliper?

[haunter]

try a huge c-clamp.....

[louthepou]

I found that the hardest part usually is removing the allen bolt. Then the rest is easier. Usually.

The sliders should come out, and if you can save the small dust boots that go on them, then great.

Getting the piston out sometimes means killing it as well; what you want to save is the cylinder part. It's not really tough, so care is important.

Once everythinh is disasembled, you need to clean everything; I sometimes had to use a dremel with wire brushes to get all the stuff out of the cylinder part and the wholes where the sliders go. Also, inspect the sliders; they sometimes are pitted with rust.

You may want to buy a rebuild kit (piston and two o-rings); around $35 I think, but better than reusing damaged o-rings.

When you reassemble, make sure you have caliper grease for the sliders, and a bit of brake oil to help the piston in (no other lube should be used).

Right side caliper - well, as far as Vision parts go, it's way up there with the rarest ones!

That's all I can think about for now, cheers

Louis

[Odium]

I had this problem with a set of used calipers I bought on ebay. I used a c-clamp and a block of wood to compress it all the way. It took ALOT of effort. I used vice grips to turn the screw for the clamp. Once it budged, I just connected the caliper to my old single-side master cyl. and kept pumping and refilling the master cyl. with fluid until it popped out. As for replacements. Check ebay for turbo Seca calipers. That's how I got mine.

[Kiwi_XZ]

I've been shouted down on this forum before for stating my preferred method, but what the heck, here goes:

The best method I have found to remove a caliper piston is with a grease gun.  Remove the tip and screw in the grease gun tube or hose a couple of threads into the brake hose port, they are usually different threads so don't force it in and only engage it by a couple of threads until it nips.  Then pump it full of grease until the piston pops out.

This method has always worked for me and the piston moves slowly (and safely) out.  Clean the grease out of the calipers with a rag then wash it out along with the piston in brake cleaning solvent, wipe the seals clean and wash them in some clean barke fluid if you are going to reuse them.

I have had new seals (both the main seal and the dust seal) made by a company here in New Zealand.  If the piston is OK then I can just fit new seals.  A kit (seals and piston) is well over NZ$100.00.

Cheers - Shane

[bikehandle]

I second the grease gun method. I made up a grease zirt that fits the caliper and plug the hose connection with a bolt. will remove any stuck pistons I have encountered, for all others I use air.

[d0n]

Good info!

I'm curious if the little rubber boot things come with a rebuild kit? While my calipers work fine, the rubber boots are damaged and are now the consistency of chewing gum. Time does weird things to rubber! I think the boots hold grease to help the caliper slide in and out?

[haunter]

Good info!

I'm curious if the little rubber boot things come with a rebuild kit? While my calipers work fine, the rubber boots are damaged and are now the consistency of chewing gum. Time does weird things to rubber! I think the boots hold grease to help the caliper slide in and out?

yes, thats the slider boot thingy(:D)

[YellowJacket!]

I got replacement rubber thingy boots from DGY for a couple bucks.  Got my caliper piston rebuild kit from them too but it wasa bout $45.00.  Worth it though since mine needed it.

David

[Night Vision]

yeah, pretty sure I didn't get any booties with the caliper rebuild kit. just the two seals and the piston

[Kiwi_XZ]

As Night Vision states the kit only comes with the piston and the two seals.  When I overhauled mine I decided to rebuild a couple of spares as well (I had at least four spare calipers in a box).  Of the six pistons I eventually ended up with, at least two were in good condition so I took a caliper and old seals out to Pacific Seals here in Wellington.  For NZ$30.00 (about US$20.00) they manufactured four main and four dust seals.

[Hegemon]

Well that turned out well.  To free the stuck I used a combination of soaking in penetrating oil for a day or two, and then using the "grease gun" method.

Caliper rebuild kits from Bikebandit, Master Cylinder Kit off ebay.  SS lines on the way.  I'm getting close!

Thanks a lot all.

[d0n]

Well that turned out well.  To free the stuck I used a combination of soaking in penetrating oil for a day or two, and then using the "grease gun" method.

Caliper rebuild kits from Bikebandit, Master Cylinder Kit off ebay.  SS lines on the way.  I'm getting close!

Thanks a lot all.

congrats!  I'm right behind ya!

[Brian Moffet]

And I have a long way to go  :(

But at least the parts to rebuild the forks and mufflers are in...

Brian

[d0n]

VR doing the fork seals is a breeze as long as you can figure out some way to hold the inner star bolt head while you turn the allen head bolt on the bottom of the fork. Pop out the dust seal, pop out the little holding clip and carefully dig out the old seal with a little screw driver.

Install new seal, old clip and dustcap. Add 9 oz. of ATF or 15w fork oil in each leg and put the caps back on.

good luck

PS if you cant find anything to hold that inner star screw... put the fork in a vise horizontally (put the caliper mount in the vise jaws), pull out really hard on the fork tube like you're trying to pull it out... at the same time, turn the allen screw on the bottom of the fork leg. Best done with 2 people. One pulling and one turning the bolt.

That worked for me on one of the forks... until I found a "tool".

If you need the tool I used give me a shout. I'll fedex it out to ya.

[Brian Moffet]

Thanks, I was going to use the method in the Haynes guide, it looked good.

Brian

[d0n]

I dont have a haynes manual yet so I improvised with advice from rov members.

dont forget the loctite red when putting the bolt back in.  :o

[h2olawyer]

The method in the Haynes works great.  Did it twice that way.  Last time, I used a pneumatic impact wrench.  No interior holding tool needed.

H₂O