I have just purchased a new set of 17" alloys. What size tyres should I fit.
215-40-17 seem popular. But I'm told Prodive fit 205-45-17 or 215-45-17, surely if the 40 profile was better they would fit that size!!

 

Prodrive fit 205/45 17 to their wheels because they have a supply agreement with Pirelli, and Pirelli do not make 215/40 17 tyres ?

 

I'd fit either 215/40 x 17 (lots of options available), or 205/45 x 17 (only a few tyre options available).

Both will keep the rolling radius within a few %, with the 215/40 being very close to that of the standard 205/50 x 16 tyre.