Tire Noise (I think)

In the last 1000 miles or so my 996 has developed a rumbling type noise. (Sounds like it is coming from the rear), It almost sounds like the tyres are cupped. It is getting worse, has anybody had this problem?. 2003 996 Targa. 18 inch factory wheels with factory Michelin Sport. 8k miles on vehicle and tyres. I did search the site but could not find an answer. My tyres are at 36F and 44R (PSI). I notice no feathering on the inside and I would estimate 50% tread left on rears and abour 70% front. I intend to run it to the dealership but would like to be kind of informed beforehand. Deon.

Tires, and performance tires in particular, tend to get louder as they wear; however, it is gradual and fairly linear, I think - like the proverbial frog in water raised slowly to boiling. It sounds like your experience was a more rapid, noticeable change than mere tire wear.

Check the inside half of the back tires. You may be down to the belts or very close..

I second what 1999Porsche says. You need to get your hands and knees dirty and really look at the inside half of the rears. This sounds exactly like what happened to me. From the outside the tires look like they have tons of tread. When I had a hard look at the inside rears, I was down to the steel belts. I was at the tail end of a 1600 mile trip, and the last 200 miles were unbearable.

Agree with the boys, tires.

Guys, Thanks for the responses. As I mentioned in my original post I notice no feathering on the inside. Now that it is light outside I pulled the car out and inspected very carefully. No steel belts showing. I do not like the Michelins in any case so I will replace them after I had the 996 at the dealer for yearly service. Deon.

If you want to isolate the noise as being from the tires, decrease the rear pressure to about 20- 25 psi and take it for a drive. Noise should be totally different.

1999Porsche911, I will try that shortly. Been looking for a reason to take her out. Will post results in a tad.

My Michelins did exactly the same thing as yours. Mine went from quiet to insane in a week flat with mileage if I remember right at about 5,000. I now have 10,000 miles and the noise is the same, the inside half and especially the first row or nearest the engine is very low on tread. My fronts have lots of life left in them, I don't know if I should just replace the rears with same Pilot Sport Ribs and maybe have alignment changed a bit so tread wears more evenly across whole width of tire?????

SYMA your alignment is probably fine that is the way the rear tires are supposed to wear on a 996

Dropped pressure by 10psi. Noise is definitely less. Increased pressure to 50psi. Noise worse. Now where to find replacements.

So it looks like it is the tires. Nothing to worry about (as long as you have safe tread left). You'll just have to live with the noise until they wear out. You might decrease the pressure front and back by 4 psi until you replace. You might try the Potenza RE750's/ I have used them for 3 rear tire replacements and they do not have the noise problem and grip in dry and wet better than any tire I have used.

Thanks JB, I know, but my thinking is that maybe a slightly bit less of camber would delay the wear, or spread it more evenly across the tire, thus keeping them a bit quieter for a bit longer. Yes? no? I have no idea.

If you do not track you war, there is no reason you cannot decrease the negative camber on the rear wheels. This will decrease the wear on the inside of the tires. - 1 degree should work.

Tire Rack

C4SSurgeon, Unfortunately I am an impatient man and want to get the issue resolved today. Maybe it is time to buy the TT as it will have new tyres on it. Everybody. Unbelievable response and feedback!!! Thanks.

Could not find tyres locally (Tire-rack it is) but found it was only the driver's rear side that was feathered lightly. (I am sensitive to all noises on all my vehicles). Maybe I am overweight. 6 ft 3 and only 191 lbs should not cause this so I suspect camber is out. Never hit a pothole or anything...interesting.. Confirmed 50% tread left on the rears. Maybe a GHL or PSE will be money better spent to kill my sensitive ears. Thanks again for all the support guys. Overwhelming!. Deon.

Actually, the more weight you put on the bacj of the car, the less the camber is. When you accelearate hard, the back end drops and the tires go flat (no camber) So maybe you need to gain a few pounds. I would have the allignment checked and if you don't track the car, have them set the rear camber to a litle less negative. Specs say -1 degree 10 inches +/- 15 inches. Maybe set camber at - 1. You will get more wear oiur of the back tires with no loss in performance.

1999Porsche911, I am a tad ignorant here but is the camber not set up to squat initially?. So if I add weight it will squat more. (As I have seen on overloaded BMW's). Interesting that you mention tracking the car but after 10 years of Porsche ownership I have joined PCA and intend to do Autocross. Daughter's influence. She is a Z club member and wants to Autocross our Cayenne. With as much tread I have on the tyres maybe I should just burn them on the Autocross track and then invest in a new set for daily driving. Thanks for informing this ignorant idiot. (I used to be a Formula V/ Atlantic driver and should know the basics. Still maintain my SCCA licence but have people set the race car up for me). Deon.

If you are going to track the car, then better decide what kind of negative camber you should have. I have never tracked my Porsche, but I have numerous other cars and I always went wth an aggresive negative setting on camber. However, there are numerous experts here on tracking and they can suggest the best allignment setttings for you based on both street and track driving. Have fun.

1999Porsche911, It still does not explain my underweight issue. I will rely on this board and my local PCA chapter to give me guidance on either my weight or the correct Camber setting. Thanks for all your responses. Deon.

I was only joking about your weight before. The alligment is done with a normally loaded car (spare, gas, etc) with normal vehicle height. The camber is set at a negative which means when looking at the wheels, the top of the wheel is pointed inward and the bottom outward. In essence, the tire is riding on the inside half of the tread. This accomidates agressive cornering as the outside wheel in a corner will flatten out and provide maximum tread to the road surface. By design, when driving straight, when you accelerate aggressively, the body of the car (along with the engine) becomes lower in relationship to the wheel's center. This forces the negative camber to reduce to the point that the vertical position of the wheel is now at 90 degrees to the road surface. You could weigh 300 pounds and it is unlikely to have much affect on the camber.

I have decided to change tires. Ordered S02-A's and dealer will fit in the morning. Soooo here is a 12 hour window for some-one wanting some fronts for free other than shipping and packaging. 2003 (I do not know how to determine whether these are Ribs or not) 225/50/ZR18 N0 Michelen Pilot Sports with about 65 percent tread left. I will pick these up from dealer but whomever wants these, have them picked up from my house arrange packaging and shipping yourself. If you are close to Tulsa OK you can come and pick them up. Deon Smith. Leave a phone number in response and I will get back to you. Be quick as I have to call dealer first thing in the morning as not to dispose of the tyres. (Car is already at dealer),