Whats the biggest tire can ya run on a16 incher? I was lookin at some 16x235/50 or 45s. I don't wanna have to modify a whole lot either due to the exspense. Does anyone know what back spacing I would need? Also I don't wann affect my gear ratio much either.
The 17's will sit just slghtly above the UCA ball joint lip, so you can run a 4.75" back space. The 16" rim will not allow more than a 4.5" back space.
With a 17x8 with 4.75" bs, I can run a 235/45WR17 without the lip rolled front and rear. Also pay particular attention to the manufactures specifications on tire size. Not all tires are the same size, even if the numbers are the same. www.tirerack.com has great specs on actual tire sizing as reported by the manufactures. On the Bridgestone RE750s that I just picked up, the specs reported on the web site are exactly what I measured when mounted.
Good luck,
66Runt is right. 17's fit better on a '66 due to the location of the ball joint. 17's will clear the ball joint and 16's have to have less backspacing. I have 17 x 8 on mine with 4.75" backspace front and rear. 225/45 in front and 245/45 in rear. No clearance problems.
If you already have 16's then nevermind.
Last time at the track I saw a '66 Mustang with 16x8 rims up front with 245 45-16s up front and 255 45-17s in the rear on 17x9.5 Yes, inner lip on the fenders was rolled but it looked sharp and nothing stuck out past the fenders.