Best tire sizes for track wheels

[DVC]

There are lots of threads about optimal offsets, how much wheel/tire can be fit, etc... but this is a slightly different question.

Tire manufacturers provide an "ideal" or "measuring" wheel width for each tire size, and it seems reasonable to assume that the wheel width/tire size that matches the "ideal" would be the best choice... and for regular street driving, it most likely would be. But for maximum grip on track (assuming a fixed wheel width) would it actually be better to run a tire that's slightly narrower to stretch it a bit? A tire size for which the manufacturer indicates an "ideal" wheel that's 1/2" (or even 1") narrower?

Here's an example of what I'm contemplating...

On my car, I know that a 9.5" wheel is at the outer limits of what I can squeeze under the front fender, so I'm trying to figure out what would be best for a track-only wheel/tire setup - the options being:

1. 275/35-18 -- typically listed with a 9.5" ideal/measuring wheel, but I feel like this tire is a bit wide for a 9.5" wheel for track use
2. 265/35-18 -- also listed with a 9.5" ideal wheel, and this size seems like it's in the sweet spot
3. 255/35-18 or 255/40-18 -- typically listed with a 9" ideal wheel (although the ranges extend up to 10")... so even with a little less "tread width" I'm wondering if this tire size would perform better than the 265/35

For the best track performance on a 9.5" wheel, which tire size would you choose?

[macdude357]

I've always heard that you want a tread width that is the same as the rim width. Since some tires run wider or narrower than others, I think it depends on what tire. A 275 RE-11 has a tread width of 9.7 inches, same as a 265 RE71R.

[DVC]

Originally Posted by macdude357

I've always heard that you want a tread width that is the same as the rim width. Since some tires run wider or narrower than others, I think it depends on what tire. A 275 RE-11 has a tread width of 9.7 inches, same as a 265 RE71R.

Thanks macdude - interesting rule of thumb...

So for the RE-71R, the 265/35 has a tread width of 9.7" and the 255/35 is 9.3" - so they bookend a 9.5" wheel by 0.2" in either direction. In this case, better to go with the tread width a little wider, or a little narrower than the wheel width?

Also interesting that the 255/40 has a tread width of 8.9", which is a sizable step down from the 255/35


*Edit to add: After some quick research, it looks like the tread width variances of a given tire size between various manufacturers goes beyond the tires being slightly different sizes. In some cases, the differences are huge, so I'm thinking different manufacturers measure tread width in different ways... which could really throw off the equation for some tires.

[bigjae1976]

You're fine if you stay between 255-275 wide tires on a 9.5" wheel. The 255s will look a little stretched.

[macdude357]

FYI, here's an article discussing this very topic:

http://www.motoiq.com/MagazineArticl...RFORMANCE.aspx

[M3 Number 86]

Also these manufacturers sand bag their specs.

[leo95se]

the standard for the e92 m3 is a 18x10" wheel. why do you want something more narrow? i think stretching the tire too much is too risky. also, agree that the tires are not spec'd very accurately.
as an example - I have my x5 summer tires stacked next to my track tires.
x5: 2 315's and 2 275's.
track tires: 4 275's.

guess which is taller? lol.

[Bellwilliam]

I am from Miata world, we hair dressers completely ignore factory recommendations.

we run 205 Hoosier (which is as wide as most 225) and most 225 on 9". and 245 on 10". 275 on 11"

and YES, we've done test and can assure you 205 Hoosier is faster (track) on 9" than 8", which is faster than 7"

this is for track. not street recommendation.

[macdude357]

Originally Posted by DVC

On my car, I know that a 9.5" wheel is at the outer limits of what I can squeeze under the front fender

I missed this part of the post in my response. Most of us run an 18x10x25 square setup for the track with 275/35 or 265/35 tires. So a 9.5" wheel would not be maxing out your capacity in the front fender. Even if you wanted to go with a staggered setup, you could still run 10" front and a 10.5" or 11" rear.

[leo95se]

Originally Posted by Bellwilliam

I am from Miata world, we hair dressers completely ignore factory recommendations.

we run 205 Hoosier (which is as wide as most 225) and most 225 on 9". and 245 on 10". 275 on 11"

and YES, we've done test and can assure you 205 Hoosier is faster (track) on 9" than 8", which is faster than 7"

this is for track. not street recommendation.

Really stretching the tire. Makes sense since you're still within square thresholds.

Curious - why do you need 275?

[Bellwilliam]

Originally Posted by leo95se

Curious - why do you need 275?

because they don't make a 305 in 15"




autocrossers love 275....
for tracks, some turbo Miata also run out of tires with 225 or 245...

aren't you surprised M3 use such a narrow tire for a 3600LB car ? if a 3,200LB Vette can take advantage of 305.....

[leo95se]

I'd like to fit a 305 around (can squeeze into the rear but not worth the lack of rotating for even wear). I didn't think a Miata would benefit from such a wide tire. Sweet

[Richbot]

I've often thought a pretty hot setup for this car would be a 19x11 with a 305/30-19 in back and 18x10.5 with 295/30 or 285/35 up front. Would need some minor fender liner massaging to fit but takes full advantage of the available space. And there are just tons and tons of factory fast cars with staggered diameters so it's not the craziest idea. There aren't many good 305+ rear tire options in 18" for these cars but tons of 19's. You could do it relatively inexpensively without taking a big weight hit if you use TE37SL's

[FrostyAZ]

I have been running a 18x11 et44 with 12mm spacer in the rear with a 305x35x18 NT01 tire. The front tire is a 275x35x18 front on a 18x10 et25 wheel. I plan to try to fit a 315x30 in the rear mainly because I want a shorter (smaller diameter) tire. The extra tire definetely helped to keep the rear of the car planted but the price you have to pay is tire wear.

In order to fit the larger rear, I had to remove the wheel well liner and grind off a little bit of seam sealer.

[Richbot]

The 315/30-18 is a nicer fit for the reason you mentioned just not many good true street tire options in that size

[FrostyAZ]

Have you fit a 315x30x18 on the rear? If so, which tire? I would like to do it with an NT01 or R888 initially so would be great to know it works.

[Richbot]

Hoosier A6 - that's a 295/30-18 up front too, this is on stock '08 springs and 8.5/9.5" wheels at stock offsets; there was lots of room around the tire in back and so I think they would fit comfortably on a 10.5" wheel and an 11 with the right 30-ish offset would probably work too. There was no rubbing anywhere. One day I will be stupid enough to go super-wide in back again but not today; car's street only now and the widest I'll probably ever do is a 295 in back. Obviously Hoosiers respond differently to pinching than street tires do, but we know from other people on this forum that a 295/30-18 on a proper 10.5" wheel will work up front as well and there's way more room in back, sooo...

[FrostyAZ]

Good to know, thanks.