Hi Jim. I'm currently running 7.5JJ Front 8.5JJ Rear rims. What is the largest width tires that I can run with this for autocross. (I'm currently running Kumho Victoracers V700's in 225/45/17 - 255/40/17).
I'm also considering another set of rims with similar specs except for the rear which is 9JJ. Could you give me your recommendations on these as well?
Thanks in advance for any help.

 

Hi Colin,

I'm not Jim, but the general principal to get the best performance out of a tire & wheel combo is to mount tires which are at the maximum width in the suggested rim width of that tire.

For example, assume that 205-55-16 are recommended to be mounted on rims from 6 to 7.5 in wide and that 225-50-16 are recommended to be mounted on rims from 7.5 to 9 in wide. Theoretically, if you need to get the best TRACK performance out of a 7.5 in. wheel you would get the best performance out of the 205 rather than the 225. In this example, despite that the 225 is a wider tire, the contact patch of the 205 would be greater on a 7.5 in wheel because the 225 would be so pinched by the rim as to make it's contact patch smaller than the 205. Also, the arched sidewalls of the 225 in this example are not as stable as the straight and parallel sidewalls of the 205.

This question should maybe better discussed in the racing and competetion forum as principals for street tires are not the same (They should be mounted on rims which are in the MIDDLE of the suggested rim width of the tire: Just ask anyone who has mounted non OEM 245-45-16 in the rear about center tire wear!)

Guy

 

i am confused now because i called tirerack and they recommended 245/45/16. it is also recomended in the important topics thread. however i am new to the tire thing and i don't know what to believe right now.

what you said about the wider tires in front did make sense to me though.