You can go on tirerack and check the exact specs of each tire. Not all 235/35/19 tires are dimensioned exactly the same (same goes for all sizes). That is the best way to ensure sizing. I would not go based upon the 997. The AWD system is different and may have higher tollerances than the 996. The sizes mentioned by Gearhead are pretty standard for the 996TT. Whether you go with 18's or 19's, keeping the diameter as close as possible is a must.

 

Thanks Nickolas,

I'm waiting for them on the 9th of February. I've already got the michelin tires. The only way to really see is putting them on... but they are definitely the closest diameter you can find!

Richard