I originally had some fairly tall 15s on mine - that is until I decided to go rear discs. Now (and ~$900 later), I have 17's, 265-60x17 ( 29.1Dia) as the 15 inch Billet Specialties wheel would not clear the Wilwood calipers on their 12" rotor. The problem I found with 17s was the lack of good tire selection as many are LT rated and real stiff.