What would cause a front caliper to "lock up" during a pad/rotor swap?
08-23-2004, 08:31 AM
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What would cause a front caliper to "lock up" during a pad/rotor swap?
A friend of mine was swapping in new pads and rotors this weekend. By the time I showed up, one side was done, and they had removed the pads on the other side. They ran into an issue where one of the pistons had extended completely. So I showed up to watch them put a C clamp on the piston to push it back (while adding a little force to keep the other piston on place.
When they were done, the new pads and rotors were installed, however the caliper wouldn't expand/contract along the three "guide pins". The other side would (as it should). They removed the caliper and installed a spare caliper that was working properly. I played with the bum caliper and a C clamp trying to get it to work, but it was frozen. It wouldn't budge at all. Anyone ever experience this before?
When they were done, the new pads and rotors were installed, however the caliper wouldn't expand/contract along the three "guide pins". The other side would (as it should). They removed the caliper and installed a spare caliper that was working properly. I played with the bum caliper and a C clamp trying to get it to work, but it was frozen. It wouldn't budge at all. Anyone ever experience this before?
08-23-2004, 08:52 AM
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When replacing pads on a motorcycle...
the "guide" pins were so worn (probably from improper caliper/rotor alignment and/or poor maintenance) the pins were actually notched and wouldn't allow the pads to slide along the pins. I installed new pins with a high temp silicone lube gel (forget the name) on the pins and made certain everything was lined up properly...works like a champ.
08-23-2004, 09:08 AM
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i have a feeling whatever went wrong...went wrong when the pad swap
was taking place. If that caliper was siezed beforehand, he would have toasted the pads and rotor, and notice severe pulling. I cranked down on both ends of that caliper to get it to move...no dice. I should have put the rear caliper tool on it to see if I could "spread" either side of the caliper. It looked like it might have been every so slightly angled, but I would think that would be difficult to do with 3 guide pins (with 2 it's rather easy to get everything ****-eyed).
08-23-2004, 09:24 AM
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Why did they add force to the other piston? That's probably what killed it.
I had that happen to me once. We had to remove the caliper, put an old brake pad over the extended piston, and use a C clamp to slowly compress it. Once it "popped" back in, it worked fine. Sure, the other piston came out somewhat, but they both then worked properly. No reason to block off the other piston as well, especially in a sealed system.
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08-23-2004, 09:37 AM
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No. Time was tight, and they didn't want the caliper siezed onto the pad/rotor.
Since a spare caliper was handy, they made the decision to swap that one in. It's possible that the caliper might have centered itself properly with one press of the brake pedal, but nobody wanted to find out the hard way that it wasn't going to do that.
08-23-2004, 09:40 AM
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It's not the pistons they had an issue with...it was the caliper frame...
The two parts of the caliper move in and out along those three guide pins. After compressing the piston, the caliper frame was frozen in place (open almost all the way). To my knowledge, they didn't touch moving part of the frame (the fixed part being the part bolted to the upright) while retracting the piston.