Which Tires for a 2002 996 TT ?

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I have 2002 996 TT which needs four new tires. My research finds only certain tires (those with the N designation) are "approved" for Porsches. All retailers and even Michelin will not reccommend any alternative.

Stock tire would be Michelin PILOT SPORT ( first generation) Front 225/40/18 and reaer 295/30/18 (N1).

I thought the Michelin Pilot PS2 would be a "better "tire compared top the Pilot sport , PS2 are stock on the GT3! ( I live in Las Vegas so I am really interested in great dry weather performance but some daily drive durabilty also). Unfortunately the PS2 is not available in a 225/40/18 with a N rating hence not reccommended. The rears are N2 rated in the stock size.

The PS2 is avaiable in a 235/40/18 with the same N2 rating as the rear and hence I can have four great traction compatible tires as Porsche recommends.

Question:

With the 235 /40/18 on the front the diameter increases from 25.3 in to 25.4 in.( 1 10th of an INCH!) Could this interfer with the ABS and four wheel drive ?

The width increase from 8.9'' to 9.3'' (less than one half of an inch). What impact will that have?

I do not want to spend this kind of money for the benefits of the PS2 to have a whole new set of problems with Abs and traction control etc.

My mechanic at the dealership told me about a Carrera Tiptronic that had shifting problems because one tire had a different N rating compared to the other three tires ( all same manufacturer) ! Are theses cars that sensitive to the wrong size or traction quality of tire?

Any comments/experience s welcomed and especially with regards to PS2 versus the original OEM PILOT SPORT ( Rib or first generation).

Thank you all in advance.

Just for the record Michelin said I should stick with the stock Pilot sport at the Original size.

Edited January 25, 2008 by Loren
Removed ALL CAPS

[Loren]

As long as the tires have same N rating are paired on each axle - you should not have a problem. As a rule of thumb you need to be within 4% front to rear.

Normally if the system is out of percentage and it is not happy it will throw fault codes. I doubt you far enough off to throw a code.

Porsche says

"If new tires are to be mounted or the tires of one axle are to be replaced, tires of the same make, the same type and with the same specification code must always be used on each of the two axles. If tires are replaced on one axle only, the different tread depth from that on the other axle can cause a noticeable change in the familiar handling. This is especially the case if new tires are mounted on the rear axle. This effect decreases with increasing tire mileage.

Maximum permissible radial runout and lateral runout of the wheels < 0.7 mm. Maximum permissible radial runout and lateral runout of the wheels with tires < 1.25 mm. Values < 1.50 mm - ideally approx. 0.5 mm - are desirable.

When replacing a tire on an axle, make sure that the tread depth of the new tire does not differ from that of the other tire by more than 30 %."

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Does that "within 4% front to rear" refer to diameter only?

Thanks

[Loren]

Yes, rolling diameter.

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Update

I fitted the 235 Michelin Ps2 N2on the front. No issues so far with dry/wet and spirited driving/braking.

Very happy with the tires although a little noisier than i remember them to be on my previous C2 coupe.

Thanks