Uneven Rear tire wear

Yesterday, I had a few hours to kill so I washed my car and decided to take the wheels off and give each one a thorough cleaning. I discovered that the rear tires are wearing unevenly. I have Michelin Pilot Sports. The center grooves on the LR are barely visible while on the RR there is about 1/8" remaining. I also have more wear on the inner but that is due to the neg camber. The car has been corner balanced and aligned and seems to drive straight. What could be causing this uneven wear. I don't think I make more right turns than left.

At the track you should be making about 360 degrees per lap more right turns than left!

I did track my 996 for several DE's on these tires so that could account for it. Other than tracking, any other possible causes?

Tire pressure?

IMO, 44 PSI in the rear tires is too high. Once the tires warm up, there could be 49 - 51 PSI back there. I had a similar issue with my first set of P-Zeros on the rear. I had to replace them at 8,500 miles. I ran the new tires at 38 PSI and got relatively even tire wear and 12,500 miles out of that set. Remember, this is just my opinion and... your mileage may vary.... without expressed written consent, is prohibited... some restrictions apply.... and all of the other happy horse-**** the lawyers concoct to cover their asses. .

When I tracked the car, I usually ran 38 hot in the back. Riding around on the street they are around 42. The curious thing is the uneven wear between left and right cause I am pretty religious about checking my pressures and keeping them even. I'm due for replacements so I don't want the same thing to happen to the new tires.

Oscar, Does your car have LSD?

44 PSI in the Rear and 36 PSI in the Front... This is good for Daily Driving and some "Spirited" driving? It is the Factory Specs... PS: i dont Track my car, but do the ocational Donuts

Nay mate....it's good for gas mileage...

Alan, I am embarrssed to say that I don't know if my silver car cas LSD. It's a 1999 C2. Was LSD standard on that model? Can I find this from the VIN?

Oscar, The answer to your two questions is the same: No! You need to check your options to see if you have a LSD and I would easily put my money on the fact that you don't. The standard LSD option code is M220, but there may be another number if it was fitted by TEquipment. You look for the option codes on the label in your original service record book or on the car. Ciao, Adrian.

If you have traction control, you most likely have LSD.

I think that is the opposite. If you have traction control, you don't have the LSD as its function is replaced by the traction control. That is true for PSM at least.

LSD did not come WITHOUT TC in 1999 model year.

I have TC and my sticker does not list the m220 option code.

Where did you get this information from? I am sorry, but I have to ask because after scouring through the manuals and the IPC (parts catalogue) for 1999 I cannot find any reference to support this statement that a LSD was standard fit for the PSM equipped Carrera 4 nor with the (ABD) Traction control (TC) option on the Carrera. The IPC only lists the LSD under option M220 and does not link it to option M222 (ABD/TC). If there is a piece of Porsche paper stating that the LSD is standard with PSM and always fitted alongside the option M222 ABD/TC for the Carrera I would love to see it. From what I have found so far to be 100% sure one must slide underneath the car and write down the transmission identification number. If the sixth digit is a "2" then it is fitted with LSD. "1" means normal differential. Ciao, Adrian. PS: Just for info: ABD/TC only acts on the rear wheels, PSM acts on all four wheels. PSM first appeared on the 996 Carrera 4, but the ABD/TC was first developed for the Porsche 928 as PSD and was offered as an option on the 993 Carrera.

I don't know if I correctly understand what your're saying about the link of the option code of the 220 to the 222, but on my 99 996, the option codes listed on the tag mounted under the hood...list both the 220 and the 222 option codes sequentially. As I said...I'm not sure if I correctly understand what it is you are trying to confirm...but both are listed there.

Chuck, By sequential I was talking about the parts catalogue listings. If two or more parts are linked as being required to be fitted together as part of an options package, the parts catalogue will list the part, then model year then the relevant option numbers side by side. Example: LSD-99-220, 222, 224, 476 The fact that on your options label you have M220 (LSD) and M222 (TC) and Oscar only shows M222 (TC) on his label confirms they are not automatically linked when ordered as options for model year 1999. Inotherwards when the dealer and customer were sitting down going through the option list and the customer said: "Oh I think I would like to have Traction control". The dealer would not be required to say: "Ah, if you take Traction control you also have to have the Limited slip diff option. You can't have one without the other". What the dealer might have said is: "Would you like a Limited slip diff to go with that Sir"?. However later on in the 996 series I believe some of these options may have been linked for certain models, but I have to check all of this out later. Thank you for this information. Ciao, Adrian.