I'm running C5 front calipers -have been for nearly 15 years. I've always noticed that they drag quite a bit, IMO. Enough that when coasting to a stop on flat ground, you can (subtly) feel them stop the car at the end of coasting.

I was working on them last night and measured 80 in-lbs (6.7 ft-lb) of tq required to turn the front left hub/rotor, and 85 in lb (7 ft-lb) required to turn the front right rotor.
If I slide the caliper off of the pads, the pads slide freely in the abutment bracket/SS shims, and the rotor spins virtually freely. The "problem", appears to be in the caliper and that the pistons don't "pull back" enough after releasing the brake pedal. Oddly, I can compress them back into the caliper body with what I feel is a normal amount of effort/force.

So....the question is, are others who're using C5 calipers able to observe a similar amount of caliper/rotor drag with this caliper? Seems like a lot, to me.

Do you ever see C5 Corvettes in your day job? Maybe take a quick moment to compare?

Thanks for replying. Unfortunately, no. I'm over fleets, so just Chev trucks, Ford trucks, busses/vans... then all varieties of equipment. Good idea, but no, I don't get to see that kind of hardware.

I guess it's fixed. I ended up pushing the pistons in/out on both calipers a couple times, and flushing the fluid (1 year old RBF600)....putting it back together and pumping the pistons/pads back out to the rotors and now the drag is significantly lower. Probably 1/4 what it was before. That's not weird....except that I typically do that as part of a brake fluid flush, annually anyway, and it's never "fixed" that issue in the past 15 years that I've had the car. But now it seems fine. (?) I'll take it, I guess.

As my auto prof used to say....."AM/FM". AutoMotive F'n Magic.

What determines the resting position of brake pads? Piston seal tension? Something else?
I wonder if the seal material changes characteristics over the years and is causing the extra drag?

I believe that it's a combination of the piston being "pulled" back by the deflection of the seal around the piston....and "rotor knock back" kicking the pads back a tiny amount from rotor run out and wheel bearing play, etc.

That is a totally believable theory. If the problem comes back, I'll change calipers.

Honestly it is amazing brake seals last as long as they do given the harsh conditions. Guessing they're not hiring from the same pool of engineers as the garden hose industry.

Man WELL SAID! I can't get a garden hose to last a freakin summer! Junk!

I agree that it's impressive what brake parts can tolerate.

How long since the fluid has been changed?

I've had a few odd cars that would drag brakes when a little heat got into the system. Root cause was water in the system. It expands with heat and applies pressure to the pads

Only definitive C5 brake issue I've heard of is caliper flex. GM went aluminum to save weight but the calipers can flex open with high pressure. In extreme instances, this wears the pads at an angle and makes braking unpredictable. Mostly roadrace guys see this issue. Basic fix is to swap to C6 base calipers. Adv fix is up the wheel size for a better designed caliper

Thanks for posting, and the thoughts/comments. I change/flush the fluid yearly w/RBF600.

I bought these calipers used (Some 14 years ago, or so) and they've dragged for the duration. I finally got irritated about it and posted.

I think that I'm just going to go ahead and swap to new/reman C6 calipers. These calipers are already dragging again -i can feel it when rolling to a stop- and I think there is something else wrong with one b/c it (the LF) "creaks" every time you apply and release the brakes. I cleaned everything up good the other day (post #3) when I was working on it, and the creaking went away for a couple days but is back again. I think the calipers are just old, been "toasted" too many times at the track and it's probably time to start over. The C6 caliper will give me a stiffer, beefier body, than the C5 caliper.... like you said.

i've got used C5 callipers on my 91 TA. New discs and pads and they were dragging slightly when warm. For me it turned out to be caliper guide pins being pitted and the receivers in the callipers being gunked up. New guide pins and a good clean out with some fresh correct grease and have been good for the past 500 miles

Copy that, and that makes total sense. Thanks for weighing in.

My slide pins slide like BUTTAH, though. They're super smooth and easy to slide b/c I did that/do that (Clean/grease) on a pretty regular basis. It's more the pistons that don't seem to be pulling back enough or on their own. But they compress fine/"normally" with a prying device, channel locks, etc, when I push 'em back in, for maintenance or new pads.