The Mustang Forum for Track & Racing Enthusiasts

Taking your Mustang to an open track/HPDE event for the first time? Do you race competitively? This forum is for you! Log in to remove most ads.

  • Welcome to the Ford Mustang forum built for owners of the Mustang GT350, BOSS 302, GT500, and all other S550, S197, SN95, Fox Body and older Mustangs set up for open track days, road racing, and/or autocross. Join our forum, interact with others, share your build, and help us strengthen this community!

Optimal tire diameter

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

237
2
Hey guys,

Please help me out deciding the best tire diameter to go for instead of guessing whats the best.

I have a 2013 boss 302, mt82 with 3.73, torsen diff and they car has cai, arh lts with offroad x, kooks catback, rear upper with mount and lower control arms with the lower relo brackets.

Your input would be gelpful and appreciated, many thanks
 

Grant 302

basic and well known psychic
Unfortunately, there is no 'best' diameter. And probably why nobody else answered yet.

Shorter tires will get you 'free' lowering of your CG and lower gearing. But the compromise is less rubber put to the ground for any given width. And sometimes that lower gearing causes an extra shift on a given course/track.

Exact opposite is true of taller tires.
 
Since you mentioned autocross in your previous thread, I'm going to recommend the smaller sidewall, 35 series tires. Even though your gearing will be a little shorter, our cars have enough RPM to keep you going in an autox course. You just have to slow down more on those huge bumps when you're on the road.
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
With my street/track car I sometimes track with my 26" street tires or wirh my 25" diameter semi slicks. With the 25" setup I get extra camber and lower car with very close gearing which is fine on our smaller tracks. You end up using 5th gear much more though.

Sent from my SM-G900M using Tapatalk
 
6,363
8,192
gear ratio vs tire diameter vs rpm comparison
3.31 3.42 3.55 3.73 3.91 4.11 4.27 4.56 4.88 5.13 5.29 5.38 5.71 6.17 27" 2677 2766 2872 3017 3163 3325 3454 3689 3947 4150 4279 4352 4619 4991
28" 2582 2668 2769 2909 3050 3206 3331 3557 3806 4001 4126 4196 4454 4813
29" 2493 2576 2674 2809 2945 3095 3216 3434 3675 3863 3984 4052 4300 4647
30" 2410 2490 2584 2715 2846 2992 3109 3320 3553 3735 3851 3917 4157 4492
31" 2332 2409 2501 2628 2755 2896 3008 3213 3838 3614 3727 3790 4023 4347
32" 2259 2334 2423 2546 2696 2805 2914 3112 3331 3501 3610 3672 3897 4211
33" 2191 2263 2349 2469 2588 2720 2826 3018 3230 3395 3501 3561 3779 4093
34" 2126 2197 2280 2396 2512 2640 2743 2929 3135 3295 3398 3456 3668 3963



(CROSS SECTION WIDTH x 0.ASPECT RATIO x 2 ÷ 25.4) + WHEEL DIAMETER = OVERALL TIRE DIAMETER

For Example:

235/45ZR-17

(235 x 0.45 x 2 ÷ 25.4) + 17 = 25.327"
 

TMO Supporting Vendors

Latest posts

Buy TMO Apparel

Buy TMO Apparel
Top