Race Tire Question

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03-30-10 | 09:44 PM

jimmacsrx7

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Race Tire Question

Hi, I am buying some racing slicks for the track car. What is the tire sidewall height at 645. 285/645/18. How does that relate to 285/35/18 etc.... Thanks,
Jim

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03-31-10 | 08:08 PM

93Fd4life

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? 645 its the % of tire width for example a 315/35/18 is 315 mm wide and 35% of 315 mm in height and then on a 18 in rim. u got ur numbers fucked up a 285/645/18 would be like monster truck size.

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03-31-10 | 08:16 PM

ptrhahn

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Per the thread in the race section, w/ race tires 645 is the actual diameter in millimeters. They don't do the aspect ratio thing like street tires. Divide by 25.4, and that's about 25.2". 285/30's are typically about 24.8" or so.

I have some Rolex GT Hoosiers, 280/640/18, and they appear to be both taller and wider than my 285/30/18 R6 DOT's.

Last edited by ptrhahn; 03-31-10 at 08:18 PM.