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More wheel questions???


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Im wondering if there is any formula for calculating appropriate tire sizes for a given wheel.I can figure what tire fits good on a wheel but i dont know how far i can go either way.Basically what i want to do is go with a 17x9 wheel all the way around with my widebody.I would like to know if it sounds reasonable to go 275-40-17 in the rear and 245-45-17 in the front using 17x11's on all four corners?Flame me if needed i just cant find things:flamedevi

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I usually just do this:

 

L = [(S/25.4)-(W+1)]/2

 

L is the length of the buldge over the edge of the rim lip in inches.

S is the tire section width in mm (ie. 275mm)

W is the width of the rim in inches (ie. 9")

 

L would be up to -.5" for a super stretched look, +.75 for a large buldge. I think around .2-.4" is a optimal, but it depends who you ask.

 

So for your 17X11:

 

Front -

L = [(245/25.4)-(11+1)]/2

L = -1.177"

 

That is way too small imho. That means on either side the tire will be in 1.1" doubt the tires would even mount.

 

Rear -

L = [(275/25.4)-(11+1)]/2

L = -.59"

 

Still a little small imho... might work. Would be pretty stretched.

 

You need something like:

 

.3 = [(x/25.4)-(11+1)]/2

 

so a 315-325mm would be nice on 11" rims. Thats my 2 cents. Someone correct me if I am wrong.

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I usually just do this:

 

L = [(S/25.4)-(W+1)]/2

 

L is the length of the buldge over the edge of the rim lip in inches.

S is the tire section width in mm (ie. 275mm)

W is the width of the rim in inches (ie. 9")

 

L would be up to -.5" for a super stretched look, +.75 for a large buldge. I think around .2-.4" is a optimal, but it depends who you ask.

 

So for your 17X11:

 

Front -

L = [(245/25.4)-(11+1)]/2

L = -1.177"

 

That is way too small imho. That means on either side the tire will be in 1.1" doubt the tires would even mount.

 

Rear -

L = [(275/25.4)-(11+1)]/2

L = -.59"

 

Still a little small imho... might work. Would be pretty stretched.

 

You need something like:

 

.3 = [(x/25.4)-(11+1)]/2

 

so a 315-325mm would be nice on 11" rims. Thats my 2 cents. Someone correct me if I am wrong.

Interesting formula. My experience is that the rim width should be approximately the same as the section width. Running your formula for a 225 on an 8" rim gives -.07 and that does not fit your .2 to .4 ideal, but I think that's what you'll find 90% of the autoxers and roadracers will use on an 8" rim.

 

Other "correct" tire sizes also arrive outside of your .2 to .4 suggestion:

 

7" should use a 205 in my experience, but = .03 with the formula

9" should use a 245 or 255, but = -.17 or .019 with the formula

 

I think the formula works, I guess for my money I'd try to get the answer as close to 0 as possible. A 305 on an 11 = .003, but I'm not sure that they make 305s, usually its 295s or 315's it seems. In that case I'd probably opt for the 295s.

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Yes, .2-.4 might be a little bulbous. Close to 0 is a good size too. Depends really I would think on how you like your setup. I would think anything under -.4" in or over .4" would be less than ideal. It also depends alot on what series tires you are running. If you have a higher profile a little more or less doesn't hurt, lower profile would have less tolerance in either direction.

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