Rotational Diameter..Help!

[trboqtro]

I just picked up a set of porsche turbo twists for my b5 a4 avant. They are 18x7.5 et50 front and 18x9 et52 rear. Now i have seen a couple of rolling diameter calculators but none of them account for stretched tires. I think I am going to get 20mm adapters all around and was thinking of something along the lines of 205/40 front and 225/40 or 235/35 rear. Any thoughts? Thanks

-Mike

[Doc@tirerack]

Only sizes we guarantee are 225/40-18 and 235/35-18. The 205 really isn't close enough at 24.4" (on a 7.5" wheel) to the OE to be a good idea, and isn't really streched on a 7.5" wheel (as it can go all the way to 8"). Main thing is that the 205 barely meets the load requirements of the front axle, so would need to be at 36 PSI all the time to be safe.