2007 Box S: rear tire increase to 275/40-18?

[paulv]

Does anyone know if I'll cause [mechanical] problems by replacing the rear 265/40-18 tires with 275/40-18 ( keeping OEM 9" wheel size width)? The 275/40's have a wheel width requirement of 9-11", so I'm OK with that on my stock wheels. I know I'll have to tweak the TPMS. Thanks.

Regards,

paul...

[RFM]

Mechanical probably not, electronically ( ABS TRAC.CONTR. etc. ) on the contrary can give problems because the outline of the orig. front wheels and the transformed rear wheels are perhaps to big.

[szentej]

Does anyone know if I'll cause [mechanical] problems by replacing the rear 265/40-18 tires with 275/40-18 ( keeping OEM 9" wheel size width)? The 275/40's have a wheel width requirement of 9-11", so I'm OK with that on my stock wheels. I know I'll have to tweak the TPMS. Thanks.

Regards,

paul...

Since the diameter of the tires are different, the difference between the two tires traveling 100 miles according to the speedometer and actual would be 101.19545726240287 miles. If this difference is outside of that allowed by the various control units in the car, the upgraded tires would not work because you would get warning lights or failure codes.

[berty987]

Why are you considering changing to a wider tyre ? I doubt you will get better grip, more likely worse grip in the wet. It may also be difficult to get the correct N rated porsche approved tyres in this size.

[paulv]

Why are you considering changing to a wider tyre ? I doubt you will get better grip, more likely worse grip in the wet. It may also be difficult to get the correct N rated porsche approved tyres in this size.

Thanks everyone for your help -- you all provided good rationale -- I'll stay with the recommended sizes.

berty: I'm really not considering changing to a wider tire -- just trying to match up a specific brand and available sizes.

Regards,

paul...

[berty987]

Personally I'd stick with Bridgestone or Michelin , The N rating means they are designed specifically for Porsche cars and in conjunction with Porsche , so they should be the optimum for your vehicle.

[Loren]

Actually N-spec as defined by Porsche means:

Porsche original equipment tires must successfully pass the tire company’s laboratory tests, road tests and race track evaluations to confirm that the prototype tires meet Porsche’s noise, hydroplaning, handling and high-speed durability requirements. Only upon successful completion of these tests, will tires be released for production.

Production tires that have passed all of the tests and received Porsche’s engineering department’s release can be branded with an N-specification.

So I think it is more of a case that they have to be "Porsche tested - and approved".

Contributing Members can read the Porsche N-Spec fact sheet in the Contributing Members forum.