Quote:
Originally Posted by Roostie
I disagree that you fail to get any benefit from wider-than 215 tire on an 8.5" rim. Shops may not even mount a 215 on an 8.5" rim because that rim is wider than the recommended fitment range for a 215. An 8.5" rim is the max width rim for most 245/50 tires. I just bought wheels and 245/50 tires, and had to get the 8.5" rims even though 9" was available, because 9" is outside the range for the 245/50 tire size I wanted.
While it is true that you will get best performance out of a tire by putting it on the widest rim within the manufacturer's fitment range for that tire, it is not true that you gain no benefit from putting more than the narrowest tire that will fit on a given rim. I have studied this issue extensively for competitive autocross.
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GRM has published multiple tests showing no performance benefit for section width exceeding wheel width. I'm not proposing a slight tire stretch for a street car, I brought it up to demonstrate the difference. That said, plenty of national level AutoX competitors appear to disagree as evidenced by their setups, so it's entirely possible there is a very small advantage. For a street tire of the class in question, it's not going to matter. I see a lot of people focusing on buying a wide tire, and not focusing on whether it's worthwhile. I also think one is better off buying a better (class) of tire in a narrower size, than shoving a wide tire on a narrow wheel. Wider often costs more.