hami

I was driving this morning in the torrential rain lots of micro debris on the road. I came to a stop at the lights when I started off again I heard this awful grating sound similar to two cats scratching a chalk board. I drove gingerly for half mile to a parking lot outside Costco tire center, parking lot being empty I took a look at the wheels couldn’t see anything. Started it up and drive around braking and turning to trying to dislodge whatever was causing this raucous! It was so bad all of the Costco Tire workers came out…manager asked if I wanted him to take a look as it sounded awful. I was about to drive it on to the ramp and I heard a click and it stopped! I have PCCB on my TTS, if a small stone was caught in the calipers is it likely to have ruined the discs? The breaks work fine now and visually to me I don’t see anything suspicious…just wondered if anyone else had experienced a similar situation and the outcome? I would expect to experience this more on the track than normal street driving. Thoughts folks? Happy Holidays!

worf928

Yes.

I have experienced exactly the same thing.

I got a bit of gravel into one of the rear wheels. I could hear it 'rolling' around. I did a quick left-right flick to 'toss' it out with unexpected results: a screeching exactly as you described. I figure the stone got lodged between the disc and dust shield. I pulled over, took a look at the rear discs and dust shield. I didn't see anything obvious so I got back in and continued on without any screeching.

In the next week or three it will be time for my yearly ritual of dismounting the wheels and cleaning everything. I'll be checking thoroughly for witness marks.

NVRANUF

It's happened to me numerous times over the 3 seasons with my 991 TT. Never on any previous Porsche though.
For me it happens in totally random locations but low speed seems a common factor. It is a bit embarrassing when it's happened to me in a busy parking lot and heads turn to see what's making all that noise.
Like worf928 has suggested, and I agree, it is most likely a stone lodged between dust shield and rotor.

Masonbrick

It happened to me this past weekend...just for a second though before it stopped. And it has happened a few times in the past. It's a horrible sound, and you described it pretty well

hami

Thank you guys for confirming. Have any of you seen the contact point, any damage to be concerned about?

Masonbrick

I've never seen anything...but it usually happened at really slow parking lot speeds while turning, or just starting to move and by the time I got to my destination I'd forgotten about it

Overdraft

Me too!...2nd day I owned the car...small stone(s) in the rear caliper I think..

Dennis C

This happened to me several times in the PCCBs on my 997 TT. It hasn't happened yet with the 991.

AKSteve

My 991 turbo is my 5th 911 and the only car I've ever owned that has made this horrible sound. It sounds like I've driven over a paint can which then gets lodged under the car's axle and dragged along for a while. It's a pretty embarrassing noise to hear coming from such an expensive car. And right when I start to get worried that something is really wrong with the car, the sound will suddenly just stop. It's happened 4 or 5 times in the last year.

Btw, I have the standard steel brakes on my turbo, not PCCB's.

philippe911

i have the same problem in gravel road, on my 17 turbo ,never before with the other 991

i think the new p zero tire is like "swing gum" and drop more gravel in the wheels arch ..................and the gravel is blocked by the rain shield and disc............

when i can ,i try to make a small rear march