Rear brake calipers engaged; cannot install rear wheel

[VCPatel]

When I had my rear wheel off during disassembly, I must have hit the rear brake, because the pads are now touching each other and they will not release.

Kind of a bummer because I was hoping to have the bike rolling tonight. Finished rebuilding the motor and installed it in the frame-- just waiting on this damn wheel!

Any thoughts on how to release the piston so I can install the wheel? I'm an idiot for hitting the brake while the wheel was off.

Cheers,
VCP

 

[VCPatel]

Also kind of in an urgent situation as I'm moving at the end of the day. I'm not keen on moving the bike without the rear wheel on there-- hoping someone can help soon.

 

[pregrid]

You're going to have to get the pads apart (obviously). Best bet is prolly to get a screw driver between the two while the bleeder is open and work it back and forth until they seperate. Keep in mind the fluid will squirt from the bleeder so be prepared for that. Another option would be to remove the pads from the caliper, compress the piston with a pair of channellocks (again with the bleeder open), then re-install pads. Should not be that difficult.

 

[FrkyMnky]

While the wheel is off, you should also bevel the edge of the brake pads a little to help with this in the future. A screwdriver between the pads will spread them apart, just be careful not to gouge them.

 

[osteoderm]

No particular reason the pads shouldn't release, but it can take some force to push the piston back and force the fluid through the master into the reservoir. Try a very thin wedge or knife-edge to get the pads started moving. Unless your cylinder/piston is in very rough shape, the pads should move okay once you get them started.
If you're on a super time-crunch, you might be able to knock the pads out of the caliper completely, mount the wheel, and deal with retracting the piston another day.

 

[osteoderm]

...three simultaneous replies with the same near-identical advice? This forum is cool.

 

[jchrisk1]

Remove caliper from bracket, install wheel.

 

[pregrid]

Remove caliper from bracket, install wheel.

Hmm, never thought of that. Easiest solution yet!

 

[gggGary]

And with the caliper off, a c-clamp will retract the piston no matter HOW bad the hydraulics are. The c-clamp will also retract a stuck 77 up front or rear caliper with it still installed. I carry a c-clamp with me when going to get "barn finds", it's saved some dragging and cursing over the years. It can be a bit of a fishing trip getting in there through the spokes, specially when the wheel is stuck.