On the track 18x8.5 wheel with 245/45s, upgrading it to 275/40s (according to the tire calculator), the sidewall, radius, diameter, circumf, and revs/mi will all be exactly the same. So does that mean it will look the same?

 

hah, i'd like to see you try to stick a 275 on a 8.5" wheel.

 

Yes, they would be the same, but an 8.5" rim is too narrow for a 275/40/18 tire. You would have severe tire buldge. In that size tire a 9-11" rim is the range that will fit, and the recommended size is for a 9.5" rim. I wouldn't try it. The widest tire that will fit that rim is a 255/45. That tire is wider than a 245/45, but also a little taller. I would run a 245/40 in front with it.

Lou