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Thread: Tires

  1. #1
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    Default Tires

    I see a lot of people run tires like 32/10.5R15 etc...what is the difference between that and the typical 255/75R15 naming convention? I guess my question is why when I look up tires online all I see is the typical 255/75R15 and I am not able to find the latter?


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  2. #2
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    Default Re: Tires

    It is just a naming convention that allows tire manufacturers to differentiate easily between sidewall heights. It used to be that most tires had a 70 or 75% sidewall (aspect) ratio to the tread. Now there are tires that have a riding on the rails effect of very short sidewalls. When looking at tires, once you hit 31" diameter you will start seeing the old nomenclature, but not always until you get past 35". There are a number of tire calculators that will convert to the old measurements for you
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  3. #3
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    Default Re: Tires

    Metric tire sizes seem to be maybe a bit more accurate than the SAE sizes.
    A 31x10.5x15 tire is rarely 31" sometimes measuring as small as 29.5", however a 245/75/16 tire or at least the ones I have are 30.5" (245mm width of tire = 9.64567", 9.64567" x 75% = 7.23" side wall height, 7.23" + 7.23" = 16" = 30.46" overall height)
    Some manufacturers are more true to size than others.

    I ran 30x9.5x15s on stock XJs with no problem, ran 245/75/16 (a true 30.5") and they rubbed a smidge.
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    Default Re: Tires

    metrics are usually closer to actual size. unfortunately, the discrepancy gets more pronounced as you go up in tire size. some "35's" measure just over 33. although some makers are reporting actual tire size along the with stated size. no real way to know until you get it on the rim, air it up and throw a tape on it.
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  5. #5
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    Default Re: Tires

    Quote Originally Posted by denverd1 View Post
    metrics are usually closer to actual size. unfortunately, the discrepancy gets more pronounced as you go up in tire size. some "35's" measure just over 33. although some makers are reporting actual tire size along the with stated size. no real way to know until you get it on the rim, air it up and throw a tape on it.
    That is why you need to do some research on your tires before you get them. Most tire manufacturers have tech info on their tires, such as height, tread width etc. But you have to visit their sites and make more than one click to find it. Another thing to look at nowadays is what load range the tires are. Most of the 16" and up rim sized tires have load ranges D and E for hauling loads and are not really suitable for our light Jeeps. So it pays to check all this out before buying any tires for our Jeeps
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