uberzz

Just replaced my rear tires with Pirelli P Zero, same size as before. My fronts are also Pirelli P Zero with plenty of tread. Only reason I replaced the rears is one got a bulge in sidewall.
Now, the handling seems to be all over the place, i.e. overly sensitive to steering input, and over all unstable feeling at higher speeds when moving car left to right.

The rear tires are "R01" rated, not "N" rated. But all the tire ratings appear identical. Is this really the cause?

Please help.

Scooby921

The "N" is not a rating. It's an OEM designation which specifies that the tire is the compound Pirelli worked with Porsche to develop for the car. It is different from their off-the-shelf rubber. It is also different from an AR, AM, M, R, LS, J, F, or other "spec" rubber compound. What you have is an "N" spec Porsche compound for your front tires and an "R" spec Audi compound for your rear tires. Both are a Pirelli PZero tire carcass, but there are going to be intricate differences in the OEM spec based on what they wanted from the tire. In Porsche's case it is a softer, more grippy rubber compound which doesn't like wet weather and gets hard and loses grip very quickly when it gets cold.

uberzz

Thank you for clarification. Would replacing fronts with matching "R" spec be best option at this point?

Scooby921

It would probably balance the car better, but based on what's happening with your rears I suspect the net change (R-spec front and rear) for the car is poorer handling than with the Porsche spec tires.

LexVan

What year is your car?
Model?
How many miles on the new tires? They need about 200-500 miles to 'scrub' in. FYI.
Check your tire pressures.

Scooby921

Good point. Brand new tires are going to need a few miles to wear off the mold release and any waxy additives in the rubber compound that have worked their way to the surface while the tire was stored on a rack awaiting purchase.

uberzz

2006 Carrera S
I would say only 100 miles on new tires. I did check the pressures after install and they were high, so I dropped them down.

LexVan

Set your fronts to about 34 and the rears to about 38. Scrub them in.

When was your last alignment?

You should have this thread moved to the 997 Forum.

uberzz

Ok, will try that.
Last alignment was about 13 months ago.

LexVan

What are the DOT code dates on the front tires?

LexVan

And what caused the "bulge"? You may have knocked out your recent alignment.

qikqbn

As mentioned, you have mixed tires mfr ratings front and rear, but you should always give new tires a few hundred miles and several heat cycles to grip and behave as they should. As mentioned there is a slippery coating applied for storage after they are manufactured. This also keeps them moist and more flexible. I always feel after installing new tires that the handling feels as if the sidewalls are softer and more flexible than the old tires replaced. There seems to be a little more sway back and forth when corning or switching lanes. I always add a few more psi of tire pressure to help eliminate that flexible sidewall characteristic while tires are still fresh and new. Once they have burned off all that storage coating they should handle better. Although I must admit my experience has only been with Michelin PS2, Supersports, or Supersport 4S.

TheBruce

Cant speak to the Pzeros as I have Ps4s and they've been amazing.

However, I would echo the comments above re mold release and tire pressure. I found mine were a little squirrelly for the first 50 miles or so.

LexVan

They are not coated for storage purposes. It's a mold release that is used during the manufacturing and vulcanization process, to get them to release.

okbarnett

new will track the road different than the old ones. they will settle down after a few miles