AlohaCS

I have a 2011 C2S with ~17,000 miles. The car has been trouble free, but recently I have noticed a very low volume sound like, "whump, whump, whump", emanating from the car's rear end. It is hard to describe, but it sounds like what a semi-flat tire sounds like. Of course my rear tires are both at 39lbs., but that "flat tire" sound is the best way I can describe the noise. It is a very low volume sound and if you were having a conversation, no one would even notice.

I have a 7 mile commute to my business and the speed limit is between 40-45 miles an hour the whole way and always with considerable traffic. Regardless of whether my PDK is in 4th gear or 5th gear I can hear the sound if I listen carefully when my speed reaches between ~39 to ~45 mph. The rate of the, "whump, whump, whump, does increase or decrease with speed, but once I exceed 50 mph or so, I am no longer aware of the noise.

My current Michelin PSS have about 8 thousand miles on them and there is very little wear. My PDK shifts hard and fast and performs flawlessly. I am stumped as to what the sound could be. To make matters worse, I live on Maui and there is a decent indie here, but any major service or warranty work requires me to ship the car to Honolulu (at my expense) to the Porsche dealer there. The cost to ship the car is really inconsequential, it's just a real hassle to do it.

Any feedback on the noise would be much appreciated.

Yet anothercrisis

I am far from an expert, but I would concentrate on the tires until I could totally rule them out. I have had this same noise on other cars and the tires usually proved to be the source. Good Luck!

Macster

Ditto on the recommendation to check the tires.

Could be a tire has developed a bubble or tread separation problem.

Or the tire could have something in the tread.

At 8K the tires are close to half worn out and these tires often go out of balance as they wear, so it could be a tire imbalance problem.

The tire lug bolts could be loose, too.

At the same time you have the car on the lift checking the tire (and check all the tires) for any signs of trouble, have the tech check the half-shafts for any signs of excessive play.

AlohaCS

Thanks for the replies. I will continue to investigate and will report any conclusive findings.

CosmosC4S

Sounds like the tires. But your issue reminds me of the noise from my Tiptronic transmission in my previous 996 C4S. Occurs at the same speed range as what you stated. I remember there was a discussion on it, and many others experienced the same unexplained noise, which seemed to be from the transmission at certain low speeds.

Hella-Buggin'

does the sound get faster as you drive faster, or does it stay constant despite speed variance?

AlohaCS

"once I exceed 50 mph or so, I am no longer aware of the noise"

The sound does increase in speed as the speed increases, however, it is only audible between the high 30s mph to approx. 50 mph.