Tire sizing question

[Jiveslug]

Hola again all. Ok, so now that Im getting down to the nitty gritty here with building a car for ITB, I need some info on tires. I can go either 14x6 or 15x6. The car can handle up to 6.5" wheel width, stock. The question that I have for everyone is, what series tires are you all running? If I go with 14s, should I do 205 55 R14, 225 50 R14, or 205 50 R14? If I go with 15s, would I do 225 50 or 205 50? Basically Im thinking that 225 is the way to go, but Im not sure about mounting a 225 tire on a 6" rim. Any thoughts? Thanks!

Jive

[924Guy]

Last I heard 6" is the biggest you can run in ITB. Seems logical you'd want to run the smallest diameter you can, for gearing; I can't fit anything smaller than 15" over my brakes, so naturally I run 15x6" rims. With those I'm running 225/45/15 Hoosiers. Yes, they do fit, no, it's not easy. We've got special power attachments for the tire machine at work that makes mounting them easy. Other ITB guys I've talked to have said they've tried it, and 225's are faster than the 205's... might not be so much the case on higher-speed tracks... YMMV!

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Vaughan Scott
Detroit Region #280052
'79 924 #77 ITB/GTS1
www.vaughanscott.com

[Jiveslug]

Hey Vaughn, nice to hear from ya. Im a total dufus. I, for some reason, thought that we were limited to an aspect ratio of 50 or higher. Dur. Anyway, the car came stock with 13-inch wheels, so clearing the brakes shouldnt be a problem. So basically, 225 series should be ok as far as fitment on a 6" rim is concerned. Its basically a matter of rolling resistance vs. cornering grip. Hmmmmm... Im going to be racing on tracks such as Willow Springs and California Speedway, both of which are high speed. Maybe 205s would be better for that application?

[924Guy]

Quite possible, of course the only final certainty is testing. You should also keep in mind that you can run a little more spacer with the narrower tires, and should, to optimize the package...

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Vaughan Scott
Detroit Region #280052
'79 924 #77 ITB/GTS1
www.vaughanscott.com

[theenico]

What kind of car? How heavy/light?

I've been known to force a tire or two into submission and get a 225 crammed onto a 6" wheel.

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Nico Prelogar

[gran racing]

I run 225/45 on 13" rims (6" wide). If your car came with 13" rims, why go to a larger diamater? Like Vaughan said, there are gearing advantages such as sticking with the 13" rims. I bring my tires directly to Hoosier and they never have any problems. The other nice thing with sticking with the 13" rims is the cheaper tire prices.

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Dave Gran
NER ITB #13
'87 Honda Prelude si

[Jiveslug]

Well, at this point, its still a hypothetical. We are looking at an 80 Corolla. Car is RWD and weighs in at 2310 spec. Standard issue wheels are 13" but are in that old 4x114 pattern that Japanese cars used to come with. Wheels in general are hard to find. 14" seem to be the most common, with 15 inchers off of old Z-cars also being somewhat available. I also have noticed that 13" tires arent necessarily cheaper than 14." Anyway, if most people run 225s on their 6inch rims, thats probably the way to go.

[gran racing]

Just be careful about using 225s other than Hoosier. I believe their tires have a bit of a cantilever to them. I had a really tough time putting Kumo Escta 215s on my old 6.5" rims (when in ITA). I was very surprised that the 225 Hoosier fit much better.

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Dave Gran
NER ITB #13
'87 Honda Prelude si

[Jiveslug]

Oh, thats not good. Im in the "financially challenged" racer set. Hoosiers are going to be a luxury. Them Toyos or Kumhos are looking better all the time. Heh. Anyway, so maybe a 205 would be a better route. I am going to be running on high speed courses (CA Speedway and Willow Springs)rather than tight, twisty courses, so perhaps the lower rolling resistance might be a good thing too....

[gran racing]

I'm not saying it won't fit, but if possible get just one and see how it works out before finding out the hard way. And yes, Toyos especially are excellent and last a long, long time.

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Dave Gran
NER ITB #13
'87 Honda Prelude si

[dickita15]

see if you can find someone running the size you want and ask for a used up tire so you can try to mount it and bolt it up to each corner before you buy
dick