torquetube

They're not supposed to move away from the rotor.

If you can spin the wheel by hand with the brakes released, they aren't dragging. You mention that it "grinds loudly" during braking, so the problem isn't a stuck brake.

Without hearing the noise it's hard to say, but I wouldn't be surprised if it just went away after a few miles of break-in.

The pistons will just extend farther to take up the clearance, like they're supposed to. Without the backing, the brakes will be more likely to squeal.

PDsVettes

He states it grinds during driving and braking, not just braking. He also stated with lugnuts holding the rotor on, it spun freely without problems. But if he put the wheel on and spun it, it made the grinding sound. Using logic, the mounted wheel could be causing the problem.

greek81

So far the conclusion is the I've got a stuck piston or 2. After tearing it down again, everything was spinning freely until I depressed the brakes for the first time and then the grinding was back. It looks like the piston or pistons aren't releasing fully to allow the rotor to push the pads slightly off.. could it just be gunked up? I didn't really clean clean it. Just sprayed it down. Is it possible if by pulling and pushing the piston in and out to free it up or once this happens it's pretty much have to be rebuilt?

PDsVettes

I'd rebuild it and be done with it. There are some Youtube videos on how to do it if you haven't ever done it before. Just be careful when you blow the pistons out. I used a 2x4 for the first blow then a 1x4 for the final blow out. I just did this on all four calipers. I had a hard time getting the rubber dust boots installed. Was easier after I figured out how to get the boots to fit into the caliper.

schpenxel

I really don't see how you get grinding from a piston stuck though. Seems like it would make the normal braking "sliding" noise, but it's hard to describe sounds over the internet so maybe that's what you mean.

Super Steve

I have a corvette 98 and found great deals on: www.crossdrilledrotors.ca

greek81

When I'm spinning by hand, yes your correct it's just the sound of the pads slightly touching the rotor but under power it intensifies and it sounds like grinding

AORoads

I can't tell you if it is the pistons, or if they're sticking. All I can say is back in the bad old days of virtually no-tech, the C2s used to either have to be rebuilt or stainless sleeves put in to remedy the stuck/sticking piston syndrome which was relatively common. So many reasons for it happening---not least of which is contaminants in the fluid, or some form of fluid breakdown resulting in water in the fluid doing its thing with standard pistons/cylinders.

You may not have that here due to what I'd call new-tech but a grinding sound when applying brakes does sound like the bad old days, OR something moving in the entire braking/suspension componentry to contact some other piece. If there are no visible shiny parts you can see from rubbing, you're kind of stale-mated into doing a process of elimination, repair/replacement, or living with it. And when brakes are making noise, that's not something I would want to live with.

greek81

Conclusion: turns out there was a hair line slice in the rubber "boot" of one of the guide pins that was causing the caliper to hang up and not fully release off the rotor.. All that for work for a little $10 part

Thanks for all the suggestions and help guys.. much appreciated

AORoads

Thanks for the update. Glad it's fixed!

greek81

I'll definitely cheers to that!!!

Thanks again