Zkalra

Hi guys,
Having a major issue - So I have fairly new rear tyres about 9 months old and say 3-4K kms, and since the front ones were worn I changed to brand new p zeroes of the correct size and spec. Both front and rear are matching. So now I have brand new from ones and older rear ones. Since the change I'm feeling the car to be fairly unstable especially at speed. I get a general feeling of understeer when I take a corner which quickly transitions into oversteer and the rear loses traction. Moreover the sense of stability is entirely missing from the vehicle. This never used to happen before and in fact the legendary Porsche traction has never let me down. Could this be due to different wear in the front and rear tyres?
EDIT - 2012 991 Carrera S, PDK, sports Chrono, all options ticked.

LexVan

Check your tire pressures. Give it a couple hundred miles for the new tires to scrub in, and wear off the mold release. How many miles so far?

bright_medal

In my opinion, I don't think it has anything to do with the difference in wear between your front and rears.

I agree eith Lexvan. I'd suggest you communicate to whoever you bought the tires from right away and then give it a short while to see if the tires break-in. It's rare, but I had the same thing happen to me (on a different car). I got a new set of tires, immediately felt unsafe, replaced them, and everything was fine thereafter. Bad set of tires. However, I think giving them a short while is worthwhile unless your tire shop would just rather replace them rather than taking liability which happened to me. Good luck!

Needsdecaf

They installed right side out? Serious with this question.

Check pressures.

When I bought my car, the rears had about 1,000 miles on them, and the fronts were new. Stable as the Rock of Gibraltar.

chuckbdc

Brand new tires are always more "slippery" than worn tires. They will get better as they wear.

But the advice to check tire pressure and make sure they were correctly installed is all good.

Note too that you should have the fronts and rears within about 5 lbs and to take in to account the cold weather.

StormRune

Chuck brings up an excellent point with the weather comment, as well as LexVan and others with the the tire pressure and scrub-in comments. Make sure you are using Partial Load pressures, Comfort setting if you wish, but not Full Load.

It's not clear where you live or what the temperatures are in your area. The P-Zeros are high performance summer tires. Once the temperatures get into the 40's, or especially if it drops near 40 or under, the tires get pretty hard and much more slippery. Could this have been a factor? Or is it warm where you are?

Zkalra

Hi, where I live the temperature is round 21 C during the day and 10-12 C during late evening. I'm talking about day time driving so temps cannot be the cause.
The tyre pressures are set at comfort and is perfect. 33 front 35 rear.

The tyres are installed correctly too. Done about 800 kms on them so far

So I'm totally confused as to what can be causing this.

randr

Are the tires the same specification e.g. N0 or N1 P-Zero

LexVan

The next consideration is alignment.

Zkalra

Hi, the tyres are the same spec exactly. N0.

teambell

Check lug nuts are properly installed and torqued to spec. If they are, return to tire shop and get their assistance.

Zkalra

Lug nuts are also fine