Interesting comparison for sure, but important to bear in mind that different tire makes / models fit and sit differently, so just generally saying X tire width is best on Y wheel width may be over-simplifying things.
The RE-71RS in 225/45R17 is listed on TR's website with a 7.9" tread width, which when compared to a lot of street tires in the same size is anywhere from 0.4-0.6" wider despite the same or similar section widths, so it sits more square / less stretched than they would on an 8 or 9" wheel.
For a more specific example, let's look at the specs of the Michelin Pilot Sport 4S:
- In the 225/45R17 size the PS4S is listed with a tread width of 7.5" with the identical 8.9" section width to the RE-71RS, so with 0.4" narrower tread it would sit and look more stretched on an 8 or 9" wheel.
- When you compare the 245/40R17's in both tires, the measurements converge a bit more - 8.3" tread width / 9.8 section width for the PS4S vs. 8.4" tread width / 9.8" section width for the RE-71RS, so the difference is significantly less.
- Also worth noting that the RE-71RS' measured tread width on the 245's is only 0.5" (12.7mm) wider than the 225's despite being nominally a 20mm (0.79") wider tire.
Now, when compared to another popular 200 treadwear rated tire like the Hankook Ventus RS4, the RE-71RS is more similar:
- In the 225/45R17 size, the RS4 has an 8" tread width / 9.2" section width, so slightly wider in both dimensions than the RE-71RS
- In the 245/40R17 size the RS4 has a 9" tread width / 10.1" section width which is significantly wider than the RE-71RS.
- The difference in tread width between the two sizes of RS4 is actually slightly more than you'd expect, with a 25.4mm wider tread for the 20mm larger nominal size.
NOTE: the measured rim width for the different sizes (7.5" for the 225's and 8.5" for the 245's) is the same across all three tires on Tire Rack's website.
It's also important to consider that some tires may tolerate a more stretched fitment better and have differing performance due to their sidewall construction, where others may not.
All the above to say that, while the comparison is interesting, it doesn't equate to a blanket "everyone should always run 225's on 9" wheels" formula. There are many other factors at play.
Only way to know for sure with different tires would be to run a similar comparison of your own.
