DB's997

14,000 miles ago, about 11 month ago I replaced my rear tires with Michelin Pilot Sport PS2s. They were rated 20,000 mile tread life, so I knew they were sticky and would not last too long. Last Friday after returning from the office I noticed that the passenger side rear tire was worn to the cord on the inside of the tire and tapered from 0 tread to a tiny bit of tread on the outside. I immediately drove to NTB to find a replacement. No tires in stock that would fit, so I ordered a pair to replace. On the way home, the tire blew out! So with a wear pattern like this I assume a 4 wheel alignment is called for? Can anyone do a Porsche all wheel alignment or would I be better off taking my 996 to my Porsche dealer for an alignment? Does the passenger side put most of the power to the road? The drivers side is not worn as bad as the passenger side.

MJBird993

If they are worn unevenly side to side, that would indicate an alignment issue to me.

My rears went out in the middle as well, at only around 10 or 12K (I can't remember) on Pirellis. At the time I attributed it to over-inflation, even though I'm always careful to stay on top of that. Maybe this wear pattern is typical for 996 and someone else can chime in?

Ubermensch

Uneven wear side to side is definitely an alignment issue. Any good shop should be able to set up a 996. what specs did you have the alignment set to? Too much rear toe-in often leads to premature wear in the rear. By bringing the measurement closer to 0 you can buy yourself a lot of tire life. You still want a little rear toe-in for stability, but not as much as most shops dial in.

DB's997

I purchased the car used in March 2011 with under 20K miles. The Pirelli PZeros on her were close to 7 years old on the rear and 5 years on the fronts. The rears wore pretty quickly and the same passenger rear was worn on the inside when I replaced it with the Michellin Pilot Sport PS2. So I am ignorant of how it was/is alligned now. I guess my question is can the 996 be aligned by just about any alignment shop or would I want to take it to Porsche? I hate to get reamed again by my dealer.

Van

Your rear toe-in might be a little excessive. But, generally, 14k miles on performance tires isn't too bad. Especially since you say they only had a "tiny bit of tread" on the outside.

rpm's S2

Anything over 10k on rear tires is good. I am constantly amazed by the number of people who risk a $1,000+ set of tires to save $100 on an alignment.

PCA is usually a good resource for a Porsche-qualified alignment shop. It is not rocket science, but you need someone with experience.

relinuca

I, too, had rear tire wear problems, and when I fitted my last set of tires I finally took it to the dealer for an alignment. Here's my advice:
>a dealer alignment costs about $175...only pennies more than an Indy.
>get a four wheel alignment!!
>be sure to tell the tech how the car is used (daily driver, track car, or?)
>save the alignment data sheet for future reference; it will show "before"
and "after" readings.

Occasional alignments are cheap insurance against premature tire wear.

relinuca

Dennis C

I recommend a four-wheel alignment from a qualified Porsche mechanic. It will cost you more than having the knuckleheads at a national chain tire store do the job, but it will be worth it. I also agree with the previous comments that 14,000 miles is pretty good for a set of rear tires.

DB's997

After investigating on the phone, it sounds like I do not have an alignment problem. Porsche tells me that it sounds normal as does my independent guy. Now I have 2 quotes for an all wheel alignment:
1) Eurocar-Werk $219
2) Momentum Porsche- $199.95
Both said the same, 14000 miles is pretty good/normal for the rears on a 996
Thinking I don't need an aligment?

SSST

I always get an alignment when I replace tires. It doesn't sound like you have much of a problem, but it's better safe than sorry. Eurocar Werks is good, but expensive. I Would let momentum do it.

San Rensho

Yep. I had my alignment changed for the track and I got too much toe in the rear. My rears had a little less than 1/2 the tread. Within 2k miles on the road, the rears were scrubbed off to below the wear bars. Bad toe will eat up the tires very quickly.

Problem is that many alignment shops won't work with you, probably because of liability issues. If you ask then to get the least amount of toe in the rear they will say, sorry, we have to set it where the computer tells us.

Macster

My experience is if the rear tires wear unevenly across the tread face the alignment is not correct. In every case with my cars it is the toe that is the culprit.

Now I do not track my cars but I do on occasion go for a spirited drive thus I do not know what track driving can do to the wear pattern.

If the car has just zero miles that is no guarantee the alignment is good. I have a new (<80 miles) 08 Cayman S aligned shortly after I bought it and the alignment was out. The car after was markedly improved.

With at least 14K miles with no alignment there has been some spring settling, some bushing degradation (though not much) assuming you have never encountered a pothole or a curb to justify imho an alignment to go along with the near tires is called for.

(Before the alignment, remove any dead weight from the car. Fill up the gas tank. Be sure any spare tire, tool kit is properly stowed/secured.)

Regarding potholes: My experience is even potholes big enough to qualify for their own ZIP code have not upset my cars' alignment though my teeth got knocked crooked from the jarring. But maybe you encounter some even worse potholes.

Also, my experience with in one case brushing a parking lot curb with the Boxster's right rear tire's sidewall not even hard enough to scuff the wheel rim (thank goodness) knocked toe out.

In another car, my Turbo, and pulling just a little too far into a hotel parking lot late one night even at slow a crawl speed and having both front tires come up against a low (lower than the air dam of the Turbo) sidewalk edge knocking the front alignment out enough to after some miles causing enough noise that I had images of bad wheel bearings when the noise proved to be from the front tires and their misalignment.

As for the difference in rear passenger to rear driver side tire wear this is explained by the car's differential type. An open diff in a turn transfers torque from the tire on the outside of the turn to the inside tire. Since this inside tire is lightly loaded it will spin/slip and faster wear is the result. In the case of USA cars of course most turns are right turns and thus the inside rear tire, passenger tire takes the brunt of this. A heavy throttle foot only makes this wear worse.

Up to you but I would advise you have the car aligned.

Where you get the car aligned is up to you but be sure you ask for beforehand and get assurance you will get it a before and after print out of the car's alignment settings.

A cheap sub-standard alignment will (my experience) eat up rear tires in 8K miles. The few dollars saved at alignment time is more than lost when paying nearly $1K for new rear tires then of course having the alignment done again to ensure the new tires last the expected 20K or more miles.

Sincerely,

Macster.

DB's997

Thanks for the information! I think I will have Momentum Porsche do a 4 wheel alignment when I get my new tires installed. While waiting for the new tires to arrive, I have the wheel from the flat over at Warehouse Tire and Wheel being straightened and refinished. Both rear wheels were bent when I purchased the car. I understand is is common on the 18 inch wheels.

MiamiC70

Just an FYI, I runn Hankook V12's and I too get about 14k miles on rears with factory spec align and "spirited" daily driving. I have been able to extend somewhat by rotating my rear tires as they are as the Hankooks are directional but can be flipped and still function fine. Doing this seems to be netting me more than 14k this time around.

Macster

If it is common for 18" wheels to be bent I don't know.

I find it hard to imagine what it would take to bend the 18" wheels of my Turbo. Were such a thing happen I doubt I would attempt to have the wheel straightened but instead have it replaced and vow to never ever do whatever it was I did to bend the wheel in the first place.

I would be helped in keeping this vow by every once in a while referring to my checkbook and the size of the check I wrote to pay for the new wheel.

Furthermore, a wheel that has been bent multiple times and straightened multiple times I would have even less faith in its integrity than that of a wheel that had been bent just once. Once bent a wheel is more likely to bend again and again as the bending and subsequent straightening just weakens the wheel material. You can take a thin piece of scrap sheet metal and bend it back and forth and in less time that you think it will crack at the bend.

A wheel is no different really save there's a lot more riding on (no pun) the wheel than riding on a piece of scrap sheet metal.

Sincerely,

Macster.