tight brakes

[stuo]

After changing the rear tire on my 2009 GV 250 I now have a very tight rear brake. I took apart the caliper, cleaned and silicone greased the pistons but it still locks up.  I'm now thinking it's the master cylinder because I put a huge amount of pressure on it when I loosened the rear axle nut. Any advice? Suggestions?

[MJR]

After changing the rear tire on my 2009 GV 250 I now have a very tight rear brake. I took apart the caliper, cleaned and silicone greased the pistons but it still locks up.  I'm now thinking it's the master cylinder because I put a huge amount of pressure on it when I loosened the rear axle nut. Any advice? Suggestions?

Does it have a parking brake that's part of the caliper? If so you may need to take the pads out and screw the piston back in.

[CROSSBOLT]

Sorry to hear about your problem. Future reference dictates to use a stout stick like a 2x4 to lock the wheel from turning while removing axle nut. You have either a "hydraulic lock" on that rear brake system or you have deformed something using "huge" pressure. First, I would see if hydraulic lock is the problem by relieving pressure in the brake line. Loosen the bolt holding the "banjo"fitting and see if fluid squirts out without squeezing the brake lever. Disassemble the rear caliper if fluid does not squirt out. Inspect all components of the rear caliper to see if any are bent out of parallel.

Karl

[stuo]

Thanks for the suggestions, gentlemen. I don't have a parking brake and the fluid didn't squirt out when I opened the line, but it wouldn't hurt to rebuild or replace the master cylinder, anyway.  I don't think it's the caliper because it happened after I put the huge force on the handle, and the brake now sticks with both the old worn pads or the new thick ones. Two by four next time, duh.

I will report the solution when I find it....

[Redk]

The pins which the pads ride on for lateral movement could now be catching on a previous wear point ?

or did I say that wrong...

Both the old pads, and pins get worn with use.
New pads could have sharp edges which could get caught on wear of the old pins, or whatever method is used to provide a stay for them.

Does that make sense ?

Good luck
redk

[stuo]

I give up: I ordered a new caliper from Leeson's: $106, shipped to my door.

[MJR]

I give up: I ordered a new caliper from Leeson's: $106, shipped to my door.

What? You were still having problems?

[stuo]

Yeah, Mike, I thought the problem was solved but when I put a new set of pads in the rear caliper they locked up again, so I bought a new caliper...problem solved. finally.

a tip: I found that most of the air in the line will bubble up out of the master cylinder as you work the handle, then it took only two openings of the bleeder with the handle pulled in (I used a bungie) to get the rest of the air out of the line, doing the bleeding without a helper.