Originally Posted by Schleprock
Your only way to do this right, and look good, is to buy 22" wheels and go with a 305/35/22 tire.
Except that this would require a 22" wheel and it will absolutely affect his performance more than just getting a wider tire.
The guy said that he thought the 45 meant the height of the sidewall, now you're getting into reading comprehension issues or just rubbing it in after he pointed out his mistake himself. Let it go.
Go with the 305/40/20 for looks and better performance. Be weary of the speedometer differences, here's a direct link to the pertinent information:
295/45-R20 vs 305/40-R20 Tire Comparison - Tire Size Calculator
You'll have more tracktion with the wider tire, it will look better. Your sidewall will actually decrease significantly on the 20" wheel with a 305/40/20 tire.
Going up to 315 it gets dicey, the problem there is that not all 315s will fit properly from what I understand. It's not an issue of actually fitting or rubbing, but the tire will get squished and cause warping and uneven wear. I know of folks running Nittos on stock rims but I'm not convinced. According to the calculator the 315/40/20 is workable and again results in smaller radius than stock wheel/tire.
I've got about 10k miles on my original tires now and I'm starting to look into this. I'm really curious if the speed differences can be "tuned" out somehow on our jeeps either at the electronics readouts or by adjusting gear ratios.
As far as the 22"s go if you can afford them and like the looks go for it. I've been trying to educate folks that even if you get a good 22" wheel that's lighter than the stock wheel things will be different and not necessarily for the good. Wider tire means more mass distributed farther away from axis of rotation, meaning greater moments of inertia for the wheel and ultimately more angular momentum for equivalent rotation rates. While I think in general these differences are in the was for guys that like to go 0-60, for those of us who care about actual road track performance this matters more. And by "good" 22" wheels I mean really expensive ones, cheap and lightweight replicas are something I'd never subject myself to. I just don't trust them at all. For pure performance staying with 20" is most likely the best, maybe getting a wider high quality wheel at 20" is the better option. Anything smaller and I'm not even sure what will fit over the front breaks on our jeeps, but you can see the Z28 camaros went with 19"s and all around 305s for performance, and it works very well.