o2bcdn

Had my 4th track day today and 2nd at Road America in Wisconsin. The rain was coming down in buckets, so got to push the stock Pirelli's in the rain and they did well. There we rivulets of running water on the track in some corners - my traction control worked overtime this weekend!

On my last outing of the morning, somehow, I punctured the right rear tire (P Zero 295/30-20) in the braking zone coming down the back straight from 125 MPH. The TPS warning bells and whistles went off and I was able to pull off the track just after the corner, no damage to the car or wheel. The car has 3500 miles, about 425 track miles and the rear tires have around 50% wear life remaining.

My question is this: will I cause any damage to the drive line by having a 50% worn tire on the left rear and a new tire on the right rear? Wouldn't want to have premature wear on my differential on any internal components. Wondering if anyone has experience with this.

BTW - turns out the local shops around Elkhart Late, WI are closed on Sunday, particularly when it's not the middle of race season. And, no one in the area carries 20 inch Pirelli P Zeros. The closest Porsche dealer was in Milwaukee and the Porsche roadside assistance worked very well - the flatbed arrived in 50mins and took me to the dealer quickly and efficiently. I then taxied to the airport, got a rental car and drove back to home to IL. Will be back in Milwaukee for business later this week and pick up the car. I see TireRack.com has the 20" Pirelli P Zeros in my size for around $500. Any ideas on what I expect the Porsche dealer to charge?

Thanks for the help!

brad@tirerack.com

We have not not had much feedback to go on with the new 991 with regards to differences in overall diameter. In my opinion I would let your dealer make the call on a full tread depth replacement. A 50% wear difference on one side has proven to not be detrimental on the 997, and one would certainly think that some degree of play has been built into the system to allow for emergency tire changes. But with that said, I'd let me shave a new tire down to match the depth of the other side just to be safe.

Give me a call tomorrow to set it up. I can shave one and get it right out. Elkhart Lake may be just overnight , two days tops.

holminator

Recommend replacing both rear tires to avoid creating a moment that could induce a spin under certain extreme driving conditions as a result of the different abilities to grip the ground. Replacing all four would be optimal (I would) but many people view that course of action as excessive.

When I use the term "moment," I mean this: http://en.wikipedia.org/wiki/Moment_%28physics%29.

97c2s993

In fact I had my car at the dealer for something else but had experienced a slow leak in the right rear a week earlier. They found a nail in the tire and recommended replacing it. Also, since there was more than 30% difference in tread between the other rear they said that according to Porsche it needed replacing too. Fortunately I had purchased tire/rim insurance so this picked up the cost of the damaged tire leaving me to pay for the other one. Tire Rack was charging $560-ish if I remember right and the dealer $8 more, so I went with the dealer for time's sake.
Expensive transaction one way or the other but at this point I have two new tires for the price of one...Since I live in Manhattan I sort of anticipate this may not be the only time this might happen, thus the insurance should pay for itself...

Scott997

Take this oppurtunity to replace the set with supersports. Much better for track then pirelli. Also great in the rain. From rural streets to Daytona, I approve this tire.

holminator

The dealer likes you. Most dealers buy from the Tire Rack or so they have confessed. Hope it all works out fine, which it will. Agree with Scott. Michelin Pilots are the best. Very easy to feel with they are at optimal temp too on the road.

o2bcdn

Thanks for the advice guys. I'm going to go for the Pilot Super Sports. Had been planning to go that route, just not so soon. Amazingly, I can get 4 PSS for about $100 more than 2 rear P Zeros. It's somewhat of a no-brainer. I'm looking forward to comparing the ride, noise and grip differences.

Should I be expecting little scuff marks on my rims after the tire changes? The wheels are pristine, not a mark on them and I hope to keep them that way. Just not sure if it's realistic. Curious if anyone has had experiences with that.

Here's a pic of the car after waxing it 2 weeks ago.

97c2s993

I didn't mention it above, but I did discover scratches on both rear rims, surely from the installation. They run along the edge in a circular motion, not around the entire rim, but a good 10 in + long... This is no doubt from the tire tool used to squeeze the rubber over the rim. I have alerted the dealer of this and that I'm bringing it in as this is completely unacceptable...my rims were pristine. They are the same as yours and I think these my be more vulnerable to this since the rim edge is not recessed but very flush right to the tire. The dealer just wasn't careful...

sfo

find a dealer with touchless fitting machine:

http://www.wheels-inmotion.co.uk/bos...yremachine.php

Zmoney3982

Just had 2 rears replaced on my 991S. Replaced with P Zeros. Can absolutely feel the difference. Did a track day on cars outfitted with P Zeros. I've felt the hold and control on city streets and on the track (including hot laps with a pro driver) and I just wouldn't buy anything else. To each his own though. Hell, there's a reason the GT3 cup car goes Michelin.

chuckbdc

Well- there is a reason that Porsche puts P Zero's on the car. I find no flaws with mine for street driving. They were outstanding on the cars that had them at the Porsche Word event that I attended. They got good reviews in the list from the guy who posted the vids of his great runs at the 'Ring.

I had found that SuperSports were an improvement over PS2s on my Boxter S - in terms of performance and price; I even prefered the way they looked-- and so am predisposed to go with them when the time comes to replace the tires that came with the car.

So I look forward to hearing from people who have actually done it and can report first hand, so I can make the happy choice when the time comes!

Scott997

You will not be disappointed. If your dealer does the tire swap there will be no scuff marks. Any random shop its a roll of the dice. They aren't use to putting on wide tires and who knows how old their tire machines are.