I've searched the archives, but didn't find an exact answer to my tires' problem. And believe me, I would appreciate an answer.

In the past, I've DE'ed with a 2000 Boxster S with stock 17" rims and Michelin tires and a 2003 C4S with stock 18" Michelin tires. I used the stock air pressure then bled down to 40lbs. hot all around. The performance and wear were very good. Alignment settings and suspension were stock.

I DE'ed my new 2006 997S this past weekend for the first time. It was at Putnam Park, as were the other times. I have 19" rims with stock Michelins. Again the alignment and suspension are stock. And I had the alignment checked before delivery. I started at stock pressure and bled down to 40 lbs hot all around. Didn't work this time.
I got 150 track miles out of them before the left front was corded and chunked on the outer edge. All the other tire outer edges were badly worn too, but not corded.
Now before I buy a new set of tires, I need some advice on 19" tire hot pressure for DE's.

My Porsche mechanic was at the same DE driving his car. He looked at my tires and didn't know why they would wear so fast. He said we could set the alignment like a GT3, but didn't know why my 997S didn't work well on the track right out of the box.

Now, could someone tell me how stupid I am for not using the right hot tire pressure and what it would be?

 

I too would be puzzled with that degree of wear.

I have lowered mine with H&R springs and also placed H&R sway bars non adjustable up front and adjustable on the rear. I was able to get 1.4 negative camber up front and 2.2 in the rear. I could go more, but for now until the 19 R comps come in I did not want to have something that would hurt road use that much.

I run MPS2 38 front and 40 rear hot. For me, that works best and I have not had problems such as yours yet, after more than 200 track miles on them. Wear is even.

Even with the additional front camber I found anything above 38 on the fronts to be UGLY.

Hope that helps.

Chris

 

If you were wearing the outside edges, I would think you need more negative camber. I know that with a 996, and MPSC's (which I know is not your setup), I need -2.7 in the front and -2.3 in the rear to get proper tire wear.

 

Your tire wear is surprising. It is not a pressure problem, at 40 hot you are in the ball park - street tires like 38-40 hot usually. Cording the outside shoulder (left side works hardest on a clockwise track) is not that unusual with stock alignment. The problem is not enough negative camber. Cording at 150 miles is odd, I have driven a 997S for two hours (dealer demo) without eating up the tires too badly. Did you get impatient and accelerate before the apex perhaps? That will eat a front tire faster. In any case you need more negative camber. For a compromise, neg 2, for more track neg 2.5 works.

Best,

 

I have a 997S too, and stock tire wear is an issue but your case is extreme.
However, I did align the car to the extreme posible with the track in mind; so I got -1 camber in front, which is still not enough, and from what my mechanic told stock camber was almost at Zero, which makes it worst in your case.
IMO -2 should be the least one needs in a stock given that it is a Mcpherson strut car. (My Elise also has -1 max but works well given that it is double wishbone configuration)

What Bob R. mentions above has a huge impact too. In some laps when I started to be too eager of lowering my lap times and accelerating earlier and earlier, there was a point at which I overworked the fronts and made them "too hot" with some loss in performance until they cool down a bit.
After 2 track days, 8 25min sessions, my 4 PS2s are now evenly worn (a lot for a 3000mi car) but all four corners have "rounded" shoulders, it is just unavoidable....

Too many corners in one direction is a big issue too with the stock tires and stock camber. I only done 1 track day at LimeRock (only one left hand corner) wiht the 997S, and I'm sure 3 track days tops will cord brand new PS2.

My recommendation is to Max your front camber to the limit the OEM suspension allows and try again and see how it goes, while taking it easier on the tight corners.

Just to illustrate how hard that outside front works (see inside front up in the air under "early power"):

 

Not to hijack, but along the same lines, I have a '87 930 that wears the left front outside of the tire. I've worked with the tire pressures and neg camber (I'm going to try -4 next time at VIR), but now I'm beginning to think that maybe my wheel is too narrow for my tire. They're 18'' BBS mag centered wheels.

The wheel range is 9-10 1/2''. My wheel is 9''. Optimal is 9 1/2''.

Could this be my problem and possibly Porshaphiles?

 

Thanks guys. I think what you have suggested is right on. Set negative camber to the max stock and quit pushing so hard in and out of the corners. I had so much brake dust on my front rims in two days, you could hardly see their silver color.
I was trying hard to see what my fastest laps would be in the new 997S, that I forgot you have to go slow to go fast. I was using the brakes to the max and accelerating out of the corners ASAP.
So I guess I'll have the camber maxed out, adjust my style and see if that helps. If not, I'll have to get some GT3 control arms installed so I can get more negative camber. But since I drive it 10,000 miles on the street a year and only 10 or 12 DE track days, I think concentrating on changing my driving style will help most. What's a couple of seconds compared to $1,500. And I could end up with faster lap times!

 

A930Rocket, you have a point. The techs at Tire Rack said going to a wider tire would help shoulder wear, but would increase understeer. So if your car currently understeers like mine, it will only make it worse.

 

Don't get me wrong, my advice and other's not necessarily mean go "slower" or don't try hard. A change in technique/approach for sure will bring lower lap times too. What happens is the "911" is very sensitive to weigth transfer. You can only demand so much grip from the tires as long as there's weight on them. So keep braking as hard as you can, and turn-in into the corner while that weight is up front. Turn-in whitout that weight transfer leads to understeer (which kills the outside front). Also, if you trailbrake you will get that much needed extra rotation from the rear, which helps the burden of the steering-front tires.

The other thing is that as soon as you get on the throttle, there's very little weight on the front, so if you are not unwinding asap the steering wheel, what you are doing is "scrubbing" the outside front, which is what may cause the premature wear.

This may sound as pretty basic stuff as you have some experience but it pays off exponentially in a 911 car. That's why is so much fun despite having the engine in the wrong place

 

Actually, I would say that trail braking would cause the most outside front wear. Hard throttle while exiting wouldn't cause as much wear because there isn't enough weight on the tire. The 996 requires a great deal of trail braking in order to turn in and that combined with too little negative camber will cause the most outside edge wear.

 

Bwah-hah-hah

Not laughing at you. You don't know how relieved I am to hear someone else has this problem. I thought I was going nuts or doing something terribly wrong. Just look a few posts down and see my thread asking about camber recommendations.

Yes, I know EXACTLY what you mean. I have a 996 C4S, but we seem to be having the same problem. I think the wear pattern is more about driving styles than actual nuts and bolts alignment since it seems to affect specific individuals more than others. You and I, and Jeeva, are the only others I know who have the same problem. We must have simillar drivng styles. I wore out the outside tread on the original and replacement P-Zeros, and the next 2 sets of Dunlop SSR's. When I switched to PS2's for the first time, I wore out the outside SHOULDER down to the cord after only 6 DE days. I was cursing the PS2's!

More negative camber is a better solution than changing drivng styles, IMHO.

 

Hears an idea of the century, Why don't you get a dedicated set of track wheels and tires. That is what I'm doing on my 997 since I don't want to destroy a perfectly good set of MPS2's. Michelin is coming out with PSCup's. The fronts are available now in 19's and the rears are due out this summer.

Just make sure you have a bank saving account for these tires.
Prices for new MPS Cup tires:
Front 235/35/19 $304 EACH ( available now )
Rear 305/30/19 $514 EACH ( available this summer in US )

These prices are in the race slick price range But they wear like iron and in the long run it's the way to go. Plus there aren't many other 19inch track tires available yet.

 

Palting, misery loves company and your experience with tires on the track is miserable, not to mention the small fortune it costs to get that education!! You're exactly right that our common driving style has a lot to do with the tire wear.
Starting with PDE, I was always taught that you should never coast; just full brake or full throttle. But slower transition from one to the other can definitely make a difference in transitioning the car from a straight to a curve and vice versa. In my eagerness to be fast, I apply the brake and the gas too quickly. Smoother input is the key for me. Instead of spinning or sliding off the track, the 996 and 997 will keep you safe, but at the expense of tire and brake wear.
In my discussion with the tech at Tire Rack, he pointed out that the non-OE Michelin PS2 front tires had a higher load rating (91 vs. 87), thicker sidewall belts and stiffer sidewall than the N1 OE Michelin PS2's. The compounds and belts across the tread area are the same. The rears OE and non-OE are exactly alike, including their load ratings.
So I decided to order the non OE set. He said the stiffer sidewalls and higher load rating should help decrease shoulder role and understeer at the same time. The stiffer side walls results in more of a harsh ride but gives you more feedback through the steering.
After talking with my Porsche mechanic today, he thinks we need to go from the current stock camber setting on the front of almost zero negative to the max of -1. And go from the current stock camber setting in the rear of -1 to -1.5. That should help and maybe cure it, if I can get my foot to work a little smoother from petal to petal!

 

Yup, it's nice to know I'm not alone. As to the cost, I got a break. The two sets of Dunop SSR's were free . I won them at autocross, so it kinda makes the pain a little less.

If it helps you any, I had my last run on the X73 with the front's at -0.45 and the rears at -1.40 degrees. You can see the wear on my camber recommendations thread. I'm going to add more negative camber for my next run.

 

I normally run the Michelin PS2's on my car at 36 /42 cold on the street. My track experience in the car is limited to Sears Point, Thunderhill, and Fernley. I start with street pressure and bleed them down to 40 lbs hot after each track session. I am an old 911 guy, so I usually carry a few more pounds in the rears. My pyrometer shows no more than 158 degrees tread temperature on the outer part of the tread for the rears, and no more than 155 on the fronts. Michelin specs call for maximum of 51 lbs inflation pressure, so you should be safe if you do not exceed that. If you are getting significant front cording on the outside edge, then you may not be running enough pressure, in addition to not having enough negative camber. But as pointed out in this thread, you may also need to adjust your driving style to lessen the "scrubbing" and abuse on the fronts. My tires are showing the effects of the time on the track, but are not blistered on the outside edges.

By the way, as far as hot tire pressures are concerned, some of the cars at PDE have the TPMS, all of them have Michelin PS2's, and the TPMS consistently shows 46 /47 while doing laps at Barber. Thats just how they run them.