I am trying to figure out what the biggest tire to fit on 17x7.5 or 18x7.5's. Could I go with 265/40/17 or 18's? or would 255/40/17 be the best. Also on the fronts would 225/40/17 or 18's bulge out of the fronts at all? I would like to get the fenders and tires pretty much flush. I have 235/45/17's now and 215/45/17's on front. I might switch these to my 87 because it doesn't have coilovers like my Formula so I can fit bigger rear tires. I have the held rear coilover kit so 255 or 265's should fit just fine on 7.5's? Let me know guys, thanks.

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1987 GT 5 spd: 2.8L
(15.57 @ 87mph)
1988 Formula 5 spd: 3.4L
(15.56 @ 84mph)
My Website: http://www.members.cox.net/rare88/

The width difference between wheel and tire should be AT MOST 2". The difference should be less than that for low profile tires like 17's and 18's. I wouldn't go wider than 235 on a 17x7.5. Consider that Chevrolet puts 245/45-17's on 17x8.5" wheels on the Corvette, and you'll have a pretty good guideline for what you can fit on 7.5" wheel.

Artherd has 265's on his Formula, but he's running 18x8.5" wheels.

Yes I agree......I'd go with 18x8 or 8.5 wheels....fits fine and looks phat!

Phil

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GTDude
OVER 25 years GM experience

Go to any tire manufacturers web site and they have suggested rim sizes for each tire. I know www.coopertire.com has this, almost all tire manufacturers have the same suggested rim sizes for thier tires.

A 255/40R17 needs a 8.5" rim minimum so that would be too big. You could go with a 245/45TR17 on a 7.5" rim, but diameter would be .7" bigger. Check site out for tire options.
ICY

I run 245/40 18's on my 18x7.5" rims. No bulging or anything, with Kumho 712's.

I wouldn't go bigger than 245 on a 7.5" wide rim, though.
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1988 Quad 4 Coupe 5 speed
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1986 GT 5 speed, 1984 SC Auto
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[This message has been edited by Standard (edited 11-29-2002).]