Help Please..... rear brake caliper piston won't compress

I could sure use some help with a modification I'm trying to finish. I removed the rear wheel so that I could change out rims - silver to black. When I try to compress the rear brake caliper piston to put the caliper back on the bike I cannot get it to compress at all it just won't budge. I have tried using the parking brake lever to turn it manually but that doesn't work. I used a C clamp to try to compress it and that doesn't work either. It seems like it's locked out for some reason. As you can see from the attached picture I've extended the piston a little bit too far trying to wiggle it back and forth to make sure it would move at all. It moves out just fine.

I don't want to remove the brake line because I figure I'll have to bleed the brakes and reading the manual that sounds like quite a chore and it sounds like you need BUDS also.

Does anyone have any tricks they know of or can give me any guidance on this?

If I remove the brake line will I have to bleed the brakes for sure?

Any help would be greatly appreciated.

Thank you,

Jed

i have seen folks do this before and i am sure someone will come to your aid soon, i can't help but someone will help i am sure.

Cruzr Joe

Hi Jed,

Re: When I try to compress the rear brake caliper piston to put the caliper back on the bike I cannot get it to compress at all it just won't budge.

Did you remove the master cylinder cap and remove some of the brake fluid? By doing this, you will allowroom in the master cylinder for the fluid in the line to go back up & into the master cylinder.

If you have tried this; then I got nothing.

Best of luck & keep us posted on how it goes,

Jerry Baumchen

What Jerry said is key. However if for some reason you do have to disconnect the brake line don't worry about having to use BUDS to bleed the brakes. BUDS is used to cycle the ABS system so that air can be bled out of it, if you are just trying to get out what may have come in during the short period of time you were dealing with the caliper the ABS system shouldn't be an issue.

very tricky with the piston that far out. It is a very tight fit and if the piston gets the slightest bit cocked it will not budge. Don't know if you have room left to push the piston out so it gets straight so you can try to push it back evenly. Draining some of the fluid helps push it back. If the o-ring is out of place this could also be a problem. You should still be fine if no fluid is leaking out. You can sometimes push with your thumbs around the edge of the piston and feel when it goes a bit sideways then push the opposite side till your far enough in to be straight...hope this help and good luck..the only other is to take it apart push the piston out clean things up and reassemble needing to bleed the system...:thumbup:

Thanks for the help everyone. I'll let you know how it shakes out.

Jed,

It looks like the piston is not going back straight. You seem to have the piston out pretty much all the way. The tolerance is very tight so, when you press the piston back you have to make sure that it is perfectly straight or else it will not go back. You do not need to remove brake fluid or open the bleeder screw. This will only compound your problem by introducing air into the system or possibly some containments like water or dirt. The fluid came out of the master and the same will go back in. The best way to put the piston back is to use a brake calliper compressor. You can get these at any auto parts store or Harbor Freight. If you are not able to fix it yourself then I think a trip to the dealer is in order.

Just asking cause I have not had mine apart but a lot of rear caliper piston are not compressed back in they half to be spun with a tool. Is there a holes in the face of the piston?

OK checked my service manual and it says Rotate the parking brake lever on the caliper to pull
back piston.
Remove and discard brake pads.

Ok

I tried rotating the parking brake as hard as I could with no luck. The piston face does have two holes, though, so you might be onto something. The dealer has it now so I can't verify.

Keep us posted to what the fix was

Sorry it took so long to get back to this but I did get my Spyder back from the dealer a couple of days ago. The biggest thing I have to report is that, according to the dealer and my experiment, the Brembro pistons screw in and out. So, all my efforts to compress the piston were never going to work. To get the piston back in you have to rotate it using the holes in the piston face. I had another issue with the caliper so it did need dealer attention. The piston would not go in enough to re-install the caliper on the disc and when the dealer took the caliper apart they found something broken and replaced the caliper. I have to give a big shout out to Powersports of Greenville for sticking with it until they found the root cause and gave me back a properly functioning Spyder.

Thanks to all of the members who commented and gave suggestions. It is a huge help to have this knowledge base of such willing members available.