brad@tirerack.com

Everything discussed so far is sound advise. Your issue could be toe related also, but certainly camber is playing a part in it also. Factory settings out back are -1.25 degrees +/- .25, so there's no doubt the car is coming from the factory sitting more on the inside shoulder. Any Porsche owner will tell you their tires wear more on the inside UNLESS that factory camber setting has been dialed out. Many don't drive the cars hard, so have it set closer to neutral to give them more even tire wear.

As for flipping, most performance tires nowadays use an asymetric tread design. The tread is designed to give you the best performance characteristics while trying to keep the tire quiet, and wear well. Outside tread blocks are usually bigger for cornering...there's more siping on inside shoulders for rain traction, etc....If flipped, there is a possibility you could see a difference in hydroplane resistance because you reversed the direction the tire was intended to channel water.

Also, one thing that has not been mentioned so far is that most of today's tires also utilize different rubber compounds as the tire transitions from inside to outside shoulder. Flipping them could result in completely different traction and increased wear. It's best to keep them mounted as marked by the manufacturer.

Macster

We are going to have to agree to disagree.

Camber as the cause of excessive inner rear tire wear gets blamed because one reason is it looks like it should cause inner edge tire wear and another reason is because every one says this is the cause of inner edge tire wear. This gets repeated and accepted as gospel.

People accept this and continue to live with excessive uneven rear tire wear as this is just way things are.

I'm saying this doesn't have to be the case, at least with Porsches. One can have a good handling Porsche, and still get (for a Porsche) acceptable tire life.

(At 20K miles for Porsche rear tire miles, this is still nearly half of the tire miles I have managed to get on other cars but other cars didn't run such soft compound tires either. These other cars were in some cases high performance cars, too. For example my 2006 GTO with 400hp. Sure, with this car I could have smoked the rear tires off the car in no time, but driving it like I did my Boxster, and like later I drive my Turbo, front and rear tire life were very very good.)

Negative camber probably plays a role in how the car handles, otherwise why have it, but it does not affect street tire wear.

As I have mentioned before with my Porsches is in every case of excessive inner edge rear tire wear toe has been the setting that from the before and after printouts has been the culprit.

The camber the rear tires have when viewed stationary is quite striking, to get sure, but once in a while I manage to get behind and follow another Porsche down the road and I can see that under way the rear tires have lost their camber and are vertical.

In the case of the cars you mention, along with other cars, OEM alignment specs have some leeway.

If I had my Porsches aligned to "spec" -- and have in the past before I became more discriminating -- the rear tire wear -- concentrated at the inner edge of the rear tires -- would be horrific. I've gone through a set of new rear tires in 8K miles just driving how I drive day in and day out.

More than once when having my Porsche aligned the tech -- if the doesn't know me -- will ask me what kind of an alignment I want. I tell him a tire friendly one but without any compromise in handling. And if the tech doesn't ask I make sure to let him know what kind of alignment I want for the car.

Of course, if longer tire life comes at the expense of a poor handling car I would choose to trade off tire life for acceptable steering/handling and road feel but so far I have not had to make that trade off.

Essentially this alignment then comes with less (or more) toe (out I think) which produces even rear tire wear with as near as I can tell no change in the feel of the car, its handling.

My advice is to if you have a Porsche that is manifesting excessive inner edge tire wear to seriously consider an alignment with less aggressive toe. Consult with an experienced Porsche tech about this to make sure he can deliver the desired alignment without any compromise in the car's handling. Also, I don't have the numbers but this more tire friendly alignment doesn't require extreme/weird toe (or other) settings, either.

With this request for an alignment that is more conducive to better tire life I believe there will be no problem, as my experience has found there to be no problem, but if the tech says it can't be done...

Frankly, though in this case I would have to suspect the tech either doesn't want to do this or doesn't know how to do this. In all but one or two cases the techs (at a number of dealerships and one indy shop) that have done the most alignments for my Porsches are quite willing to discuss alignment with me and work to align the car to deliver meet my requirements: Optimum tire life and this includes even rear (and front) tire wear, but with no compromise in road feel, handling, steering response or stability at any speed.

Wayne Smith

Small changes make big differences.









Both rears wore quickly with DD driving and some 500 mile freeway trips.

New tires were installed and the above specs were performed on the alignment.

Both are wearing fine with 4K miles on them so far.

The new tires are being inspected weekly by putting the car in the air. It is hard to see this stuff with the car on the ground.

Mine is a .2 C4S. YMMV. I am not recommending the above settings. Your driving style and travel routes will affect your outcome. My settings may still change. The above is for example only and to show the small differences. West Marin has some crown on her back roads. The asymmetry is to allow some fun with the car on my playground. I suspect some tuning is still needed.

Wayne Smith

Per the above post, here is a shot of the left rear tire taken from the back after 4K miles.

You can see that there is more dust (pressure) to the inside. Tires are 38 psi cold (with 50F ambient). The car is generally lightly loaded.

Yes, the pressure is a bit high ... compensating for mostly freeway driving. I AM staying off of the edges this way and am still watching to decide if I want to tweak or not.

Of the 4K miles, only 10% of that was spirited back roads. A couple thousand was long haul.

There is 10/32" tread left still (effectively zero wear to date ... a bit unusual).

These are PSS tires. The tread is symmetric. I remember when radials first appeared in mass in the late 60s. We changed from cross rotation to front back rotation. Because of the difference in the plys we were concerned with changing direction once a rotation pattern was created. I lightly implied don't swap sides in my first reply. To be true to myself, I should have simply stated don't.

Feel free to correct me anyone if things have changed in the tire industry since my participation.

jhbrennan

Not sure it makes any difference but the PSS -" The Pilot Super Sport features an asymmetric design"

Wayne Smith

The dealer quoted me a better price than anyone else, no shipping, and one day service. I dropped the old ones off, not wanting to drive on them (alignment done the next day). I expected them to be right and left. There were no arrows. I expected them to have an inside and an outside. No markings or indications. What can I say?

Are you saying that there are different versions of the PSS? Or did I miss something on my tires?

Note: I've tried to post a picture of a page in my history book with a picture of the tire new on the wheel with tag. I am getting system crashed errors. I've had this happen before and include the picture without an image in my text. Other times nothing. If there are multiple images, that is the cause.

ADias

Michelin Pilot Super Sport tires are asymmetric with different rubber compounds and tire structures outside/inside. Each tire is marked 'OUTSIDE' on the edge of the outer sidewall.

jhbrennan

Don't know if they have changed but I bought mine at Wheel Enhancement about 6 months ago and they are marked "Outside" on the sidewall - not real big lettering but it's near the DOT info on the sidewall. Either you didn't see it on first look or you mounted inside out...bet you just didn't see it.

jhbrennan

You're a better photographer than I am

Wayne Smith

Absolutely correct - both tires. So they were correctly installed on the wheels.

Thanks for making me smarter. When I got them home I was looking for rotational arrows (not found on either side) and I was not bothering to read the writing! It was exactly where you said it would be (of course).

Damn, it's been a long time since I've mounted a tire!

mdrums

I have Yokohama tires too..they are directional so no you can't reverse them on the wheel because the tread is designed to shed water.

How many miles on them? The rears will wear the inner part o the tire faster but you should have your alignment checked.

For street driving and to stay in spec I suggest
FRONT .75 to no more than -1 degree camber per side front with zero to slight .02 degree toe out
REAR 1.25 to no more than -1.4 degree negative camber per side with 1.5mm or .14 toe in

Kuhl997.2!

Thanks every one for taking the time to help me out with my tire question. I stopped by the local auto parts store and picked up a tire depth gauge and measured the tread wear difference only to find out there is virtually no difference 7 mm across the tread on both sides of the rear tires and 9 mm across the tread on both sides of the front tires. It is some kind of optical illusion the tires are wearing on the inside more than the outside like the blue/black or white/gold dress thing. I actually had the right answer when my wife asked me which color the dress was. I said it looked like her husband washed her dress incorrectly and he owes her a new dress, gosh I am sorry I was just trying to help lets go out tomorrow and find a nice replacement and we will take the Porsche.

Cheers

Wayne Smith

Very well done on the dress!

BIG smoke

To the o/p
Is the car lowered?
How old are the tires?
Mine last about a year, and 10,000 miles back, 20,000 front.
Glad you sorted out your tread wear optical illusion.
Snowy and slushy here. Heaves in the road are tectonic.

P911CS

OHHH SNAPS!!!!! Good to know you walked away from that