Tire rack test on tire width vs wheel width

[Tatsu333]

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.

[RedReplicant]

The overall general point of this test is that maybe the fairly popular advice of spoon on the widest tire you possibly can isn't actually the fastest option, not that you should specifically run x size on y wheel width.

[Tatsu333]

Originally Posted by RedReplicant

The overall general point of this test is that maybe the fairly popular advice of spoon on the widest tire you possibly can isn't actually the fastest option, not that you should specifically run x size on y wheel width.

Right - I get that, but not everyone will take it that way.

[Lucky Ookami]

Thanks for pointing out the tread width!

[Ohio Enthusiast]

TireRack continued this test, released a video of the results -

They narrowed it down to:

1. 225/45R17 on 8" wheels
2. 225/45R17 on 9" wheels
3. 245/40R17 on 8" wheels
4. 245/40R17 on 9" wheels

All on RE-71RS. They also used Hawk DTC-60 pads with Centric blank rotors and camber bolts for -2* front camber. No other alignment data was provided, but they did say they had the same alignment on all test cars.

This time it was on a larger track (looks like GingerMan by the track outline in the video thumbnail (edit: and by the GingerMan signs on the track footage)) with the wider wheels being faster, but no real difference between the tire widths:

1. 245 on 9" - 1:45.33
2. 225 on 9" - 1:45.41
3. 225 on 8" - 1:45.96
4. 245 on 8" - 1:45.96

This goes against the common wisdom of "wider tire is better", but is consistent with the previous TireRack test.

[cmiovino]

Originally Posted by Ohio Enthusiast

1. 245 on 9" - 1:45.33
2. 225 on 9" - 1:45.41
3. 225 on 8" - 1:45.96
4. 245 on 8" - 1:45.96

This goes against the common wisdom of "wider tire is better", but is consistent with the previous TireRack test.

I wouldn't necessarily say it goes "against" wider tires being better. Both sizes on an 8" wheel set the same time and 245's were slightly quicker. The 245's aren't "slower" lol.

Although, all of it's within the noise. Different style drivers might prefer different setups.

What's very interesting for me is seeing how much wheel width plays a part in grip. You'd rationally think tire width makes more of a difference and wheel width would help, but it's like 95%+ wheel width making the difference.

The SCCA must have known this well before when only allowing stock wheel widths for street class, but allowing any tire size. For example, the twins get ~7.0 - 7.5" wheels depending on trim level and can go to 9.0 in STX trim. A 245 on 7.5" most run in DS is going to be slower than a 245 on a 9" in STX for sure with the data we're seeing.

[Ohio Enthusiast]

Originally Posted by cmiovino

The SCCA must have known this well before when only allowing stock wheel widths for street class, but allowing any tire size. For example, the twins get ~7.0 - 7.5" wheels depending on trim level and can go to 9.0 in STX trim. A 245 on 7.5" most run in DS is going to be slower than a 245 on a 9" in STX for sure with the data we're seeing.

This is a very good point! Do other organizations have similar limitations?

[autoracer86]

I'm planning to go with a 225/45/17 on a 9in wheel. I rather a 245 but tire shopping in Ireland is not easy lol. At least I won't be losing too much performance

[Racecomp Engineering]

The wider tires do handle heat a bit better though, something to keep in mind for track people doing extended sessions. Also, what's fastest for 1 lap may to some extent be course dependent (though I'd almost always take the 245 on the 9 inch wheel from this test).

I do agree with the video that 225/45/17 on an 8 inch wheel IMO is the most fun and jsut "feels" great all around.

- Andrew

[RedReplicant]

It is also worth noting that a wider tire also gives you more sidewall compliance, which makes wheels less consumable.

[ruturaj001]

Originally Posted by autoracer86

I'm planning to go with a 225/45/17 on a 9in wheel. I rather a 245 but tire shopping in Ireland is not easy lol. At least I won't be losing too much performance

Might not be a good idea for street, 8.5" would be in between and generally within suggested rim size by tire manufacturer.

[ZDan]

I’m running 225s on 17x9 this year, fits better than expected really. Doesn’t look stretched, at least if tires have some rim-protector bulge. A052s don’t, but still looks fine, and performance is pretty much same as 245 on 9”

[autoracer86]

Originally Posted by ruturaj001

Might not be a good idea for street, 8.5" would be in between and generally within suggested rim size by tire manufacturer.

Any suggestions on 8.5in wheels ? I was shopping around for 8s but it’s hard to find something I want as much as the 17x9 from apex.

[ruturaj001]

Originally Posted by autoracer86

Any suggestions on 8.5in wheels ? I was shopping around for 8s but it’s hard to find something I want as much as the 17x9 from apex.

If you are okay with bronze color then konig heliogram