Rubbing sound under light braking

I've done some searching on this site and around the Net, but haven't found a solution to the issue I'm seeing, so I wanted to get everyone's thoughts. I have a 2003 C2 with about 60,000 miles on it. The car is largely stock, and I just had a set of Feal 441+ installed to replace the stock struts as the fronts were worn out. I noticed that under light braking I'm now hearing a light rubbing sound - almost like a sigh - coming from the right front of the car. The sound stops immediately after I take my foot off the brake pedal. It is not a grinding or squealing sound and I'm not feeling anything through the brake pedal like I would expect with the ABS engaging or the pads grinding into the rotor. I do not hear this sound while otherwise driving, so it seems to be brake related. I took the car to my indy who looked it over. He didn't see anything rubbing that would cause the sound, and the car isn't so low that it could be the tire rubbing on the fender liner - I have the coilovers at pretty much their max height. At that time, he thought it might be the pads since those were getting very close to end of life. I had him replace the pads (rotors too since they had a significant lip), but the sound is still there - no change from before the pad/rotor replacement. I took the car back into my indy so he could look it over closer. He says it may be an issue with the caliper sticking as the front right tire does not spin as freely as the front left tire. He's going to drive it a bit to try and replicate what could be causing the issue and get back to me. While a sticky caliper makes sense on the surface, it seems to me that this rubbing sound would be occur more than just during braking as the pads would constantly be rubbing. It also seems that even if there was a delayed response with the caliper the sound would continue for a little while after I take my foot off the pedal. As it is now, the sound stops as soon as I take my foot off the brake. The only thing that comes to mind is that perhaps the tire rubs on the liner when the nose drops during braking, but I don't hear the sound during a hard stop. I would expect to hear more rubbing during a hard stop as the nose would likely drop more than it does during light braking. I'm interested in whether anyone else has come across this before. If so, what needed to be repaired? Any thoughts would be much appreciated! Thanks in advance!

Does it occur at a sort of speed and braking pressure that you could do driving backwards without risking anything? Then the front coilovers would extend and when the noise is gone you know it comes from the struts compressing under braking driving forward.

I only notice it at slow speeds coming to a stop at an intersection. Haven't tried in reverse...that's a good idea and would help rule out the tire rubbing under compression. Thanks!

Unlikely cause is the wheel bearing. I had a squeak/rub/grind/creak sound from my left rear, and it ended up being: something back there was not fully tight. The shop that could not figure it out took the wheel bearing out, removed the half shaft, put everything back, and torqued it all to spec. The wheel bearing needs 340 ft.lbs, and I suspect something on my car was loose.

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It's really tough to diagnose without hearing, seeing and feeling it in person. But your indy did say everything checks out with the brakes but there is a possibility of a caliper piston possibly sticking. Hardtailer's suggestion is a good one. But if I had to guess, it may be a piston. The car is 19 years old and calipers do eventually need to get rebuilt. Crap gets in there and the seals decay. Salt, dirt, ground up sand and gravel. Since your indy said the brakes check out, you can always go to a big open parking lot and do a few high speed braking exercises to exercise the pistons. Maybe if its a piston thats sticking, it may help to lossen it up. No guarantee. Just make sure that nothing is in front of you that you can hit in case there really is a problem. Brakes are pretty damn tough and durable, but with age, pistons can get stuck and as a result, do need to be rebuilt. Hope it helps. Let us know what you find.

Thanks all for your thoughts! Car is with my indy and he is looking it over. I'm interested in what the cause is and will let you all know what the final result is. Can't wait to get back into the car and put it through it's paces with the new coilovers!

Did you ever get a verdict on this? I was following because I had a noise that sounded sort of like brake rub but it was happening most of the time regardless of braking. Plus Feal coilovers. Finally pulled the rotor off and found that the hub was less than quiet. No play or rattling, just sounded dry. My indy pulled it and confirmed -- no grease in the bearing, it wasn't falling apart (yet), just dusty rusty metal on metal. Popped in a new one and the sound is gone. Maybe the coilovers (or just plain new suspension) are a more direct connection that makes it more noticeable.

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I had this noise appear also after my Feal coil over install, I assume it is from the lack of rubber isolation on the strut mount that makes it more noticeable.

So...the saga continues. We're going the route of a caliper rebuild. I found that I still hear the rubbing sound when raking in reverse, so less inclined to think this is an issue of the tires rubbing when braking especially since I only hear the sound when braking at slower speeds driving in town. The issue is now obtaining the parts for the caliper rebuild. I ordered the seals but there is some issue with the manufacturer, so they are on backorder. I won't be driving the car for awhile anyway, so the delay isn't going to be that big a deal, but more of an annoyance as I'm interested in what is causing the issue more than anything else. Interesting that others have had a similar experience after installing coilovers, but given the age of the car a sticking piston seems to be a reasonable source of the problem. Hopefully that will take care of the issue. Once the rebuild is completed, I'll let you all know the outcome. Believe me...I'm as interested as you are! Thanks again for all the input!

You can obtain seals and dust boots from racingbrake.com to fit any Brembo caliper, including the ones on your Porsche. I have used their seals and dust boots and could not be happier. And they actually have them in stock!

Thanks for the heads up on that! I'll take a look at that site. Hopefully, my original order will come in shortly, but definitely good to have a back up!

If tyres rub against anything you see marks where it does so (apart from the tread obviously). Have a look at the inner tyre side wall when you start to remove the brake caliper for its overhaul. I agree with you that rubbing is the source of the sound but it's an easy check (and easy to forget).

Crank up the volume on the stereo! You will drive yourself berserk.

That was my course of action when I get back in town and eyes on the car!

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That's exactly what I've been doing! Since this was a new occurence, I figured I would check in with the braintrust!