Removing caliper pistons

[Brad_G]

Been working on a project '03 Road Star over the winter. I noticed when removing the rear wheel that the caliper wasn't releasing as it should. So figured I'd get a rebuild kit and all would be good. I've got the caliper off and I split the two halves. I started with an old bicycle tube on the piston to try and not damage it. But it won't budge. Any suggestions on ways to get those pistons out without damaging the caliper housing?

[Kurf]

Use a grease gun ( if you call it like that) and let the grease push out the pistons. Works all the time for me. Offcourse degrease the hell out if it before assembly

[Lug Nut]

I use compressed air but be careful little launch that piston like a bullet. I wrap a towel all the way around it and then use the compressed air. Definitely pops right up

[Brad_G]

Thanks. I'll put the halves back together and see what happens. I have a suspicion I'll have to install it on the bike again and use the hydraulic pressure to push them out.

[brianmac]

only push and clean and replace one at a time, so u can push out the other, use c clamps to hold them in while using air and a rag to catch

[D-Fresh]

As brianmac and others have said, you don't want to launch a piston. The other issue is, if you push one of them all the way out you will loose all your pressure so its good practice to use some wood shims in the caliper so you don't push one all the way out before the other ones start to come loose also.

[Brad_G]

Yep this is an excellent point. Hoping to work on it tonight. I'm guessing air pressure alone won't be enough but I'll try as I have a compressor here along with the caliper. If air won't do it I'll probably head over to the shop where the bike is and use the bike's brake system. I need to flush the old fluid out of the system anyway. But a series of thinner and thinner spacers it is!

[Kurf]

Reason I use grease : will not shoot the piston out and seems to be stronger than air pressure ( air compresses more )

[Brad_G]

what do you use for a fitting to attach the grease gun?

[Shores]

what do you use for a fitting to attach the grease gun?

I would guess he attaches it to the bleeder zert.

[Kurf]

Correct!

[Brad_G]

Reason I use grease : will not shoot the piston out and seems to be stronger than air pressure ( air compresses more )

This ended up being a great suggestion for my situation. Thank you very much!

I would guess he attaches it to the bleeder zert.

This was my biggest hangup when thinking about it. I was focusing on the banjo bolt. But your are correct Shores, the bleeder valve is a direct fit for my grease gun. I had to unscrew the grease gun end halves to get it to release when I was done...but having an extra hand was also a benefit.

I had to grind/file a few washers to make a spacer to plug the banjo bolt. But once I figured that out everything worked well. Thankfully the pistons on the banjo side moved first and got them out. I separated the caliper and took a couple c-clamps and the little o-rings that go between the halves to seal off those ports. That allowed me to work on the remaining 2 pistons. A 3rd c-clamp helped make sure one piston didn't get too far ahead of the other. Took a while but everything is apart now.

The only downside is cleaning up all the grease when done. Now just awaiting the rebuild kit so I can re-assemble. Thanks for all the input everyone shared.

[Kurf]

Glad it worked out. Sorry if I was not clear enough about the execution…. Good luck degreasing..

[Lug Nut]

Air = no degrease Popped mine out one at a time in 5 seconds
Brake cleaner, rag and very fine emery cloth
New seals....put back in with brake fluid as lube

[Brad_G]

Yeah the air would have been cleaner for sure. With the difficulty I had getting them out wasn't sure if I could get a good enough seal (ie = enough hands to hold everything ) so opted for the grease method.

[Shores]

I just use compressed air with my rubber tipped nozzle attached to the hose and pressed it into the hydraulic hose hole. That's what she said anyway.

[Brad_G]

As long as she was agreeable... But were the pistons stuck? This bike the brake was dragging pretty good. I can now see why 20 year old fluid and a lot of sitting can cause issue.