Is there a general rule for picking the optimal tire for a given rim size? For instance, I have a set of 14X6 rims and some 15X7s. I'm planning on using the 14X6s for autoX. What would be the best tire for this size rim? I know that typically a 6" wide rim will be fitted with 195 tires. Should I go with that or should I use wider tires like maybe 205s? Will I have problems with sidewall flex or something like that if I go too wide? Thanks for any help.

 

You can run 225 on those rims if you want.

If you run falkens(which you want if you nwer to the sport) or Hoosier or kumbos sidewall flex will not be a problem.

 

wow! I can go as big as 225??!! Damn! Would tires that wide be recommended for autoX? Thanks for the info!

 

stock class Ef run 225 on the front all the time. the car will corner better with the large tire and but will feel very vague due to sidewalls being at an extreme angle.

You also have to find a shop to mount the tires which will be very difficult.

 

So, I take it you feel that 225s would be the optimal tire size? Do you have any scrubing issues or anything like that? I'm going to assume that you don't since you use that size for AutoX. Do you have any pics of the setup? Thanks

 

Lots of contact patch is good, and thats why you see the 225s.. I run 225s on my 13x5s.

Recomended? Only by those of us on this board. Rim companies, and tire companies say hell no.

There are three issues when people say no.. (other than "its not safe" or "too hard to mount".. blah racing isn't safe, or easy)

1) Getting heat into the tire. a wider tire has more area of course and in theory has more trouble building up heat. But in 90 Seconds I can have 225/50/13 Hoosier autocross tires in the high 140s, and within 3 across the tire. I dont see the issue with getting heat if you are driving the car how it needs to be driven, and have the suspension right. With Azenies of course, its easy to overheat.. so perhaps it would actually be an advantage to have more tire.

2) When putting the wide tire on the rim, it tends to twist it in weird ways.. and i am told it hurts the area of the tire actually making contact with the ground. It does make them look weird, but see the tire temps above for "not making contact" within 3' thats pretty dang good for a tire not using all of itself.

3) Rubbing, which you mentioned. Yep. They rub. Without spacers i will smell burning rubber. But.. my 1987 CRX has rub marks on the inside of its wheel wells, and the biggest tire i ever ran on it was a 185/60.

So there is what to consider. or some of what to consider anyway. I hope that helps a little.

Jon K
http://www.seat-time.com

 

wow. 225s on a 5" rim!!?? That must look pretty unique... It works though huh? So 225s on my 6" rims should be ok? I'm pretty anxious to try that out. Thanks for all the help!

 

yep.. 225s.. that seems to be the general reaction though.. people are surprised.

Robert Carpenter was the first to do it though, i was just playing monkey see monkey do. He took the heat a BUNCH worse.. people telling him he was an idiot and such. It's funny people dont say that since he has a couple of national championships under his belt running that set-up.

as far as it "working" It might not for every car.. CRXs seemed to be way under tired for the fender space. I have not tried the super wides on anything else.. When i swapped to the S04 I knew it was wider so i bought 1 tire at first for a test fit, when it did fine then I bought the other 3. You might want to try something like that. btw.. the S04 still does rub.. but not much worse.. so you might expect a "little"

Jon K
http://www.seat-time.com

 

Optimal would be to have a 8 or 7 inch rims.
but 225 will work on the 6inch wide.

 

I cant find rims for my Celica so I use the stock ones for road racing, but I always ran it with 205s I was scared of using 225 on a 6" rim. I going to try it soon but anyone know what PSI should you run. I run 28 PSI with my 205 Kumohs

 

28 seems pretty low for roadracing. I tried 36 on my SSC neon once on Kumhos and 10 min later i had a blistered set. Might want to start higher, then see what the temps do.

Jon K
http://www.seat-time.com

 

most of the people start at 27-29 PSI and buy the time we end the race its about 35-40 PSI