240/40/18 on a 7.5 inch wide wheel?

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  1. #1
    Join Date
    Mar 2001
    Jacksonville, FL
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    240/40/18 on a 7.5 inch wide wheel?

    Hey guys, anybody know if I can fit 240/40 tires on a 18x7.5 wheel?

    I wanted to switch over to 240/40/18's from the factory 235/45/18 due to the lack of tires available in that size. 240/40 offer a much larger range of tires. Not to mention cheaper too! Also will the overall diameter change by much?

  2. #2
    cone junkie PseudoRealityX's Avatar
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    Jul 2002
    Gainesville, FL
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    That's enough rim for a 245, so I don't see a problem.

    -93 MR2, #129 ES

  3. #3
    Registered User
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    Apr 2005
    Pinellas Park, Floridrizzle
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    Quote Originally Posted by Sam_I_am
    240/40/18's from factory 235/45/18...will the overall diameter change by much?
    Your tires would look a little thinner and also slightly wider.


    Section Width

    Following the letter(s) that identify the type of vehicle and/or type of service for which the tire was designed, the three-digit numeric portion identifies the tire's "Section Width" (cross section) in millimeters.

    P225/50R16 91S

    The 225 indicates this tire is 225 millimeters across from the widest point of its outer sidewall to the widest point of its inner sidewall when mounted and measured on a specified width wheel. This measurement is also referred to as the tire's section width. Because many people think of measurements in inches, the 225mm can be converted to inches by dividing the section width in millimeters by 25.4 (the number of millimeters per inch).

    225mm 25.4 = 8.86"
    Sidewall Aspect Ratio

    Typically following the three digits identifying the tire's Section Width in millimeters is a two-digit number that identifies the tire's profile or aspect ratio.

    P225/50R16 91S

    The 50 indicates that this tire size's sidewall height (from rim to tread) is 50% of its section width. The measurement is the tire's section height, and also referred to as the tire's series, profile or aspect ratio. The higher the number, the taller the sidewall; the lower the number, the lower the sidewall. We know that this tire size's section width is 225mm and that its section height is 50% of 225mm. By converting the 225mm to inches (225 25.4 = 8.86") and multiplying it by 50% (.50) we confirm that this tire size results in a tire section height of 4.43". If this tire were a P225/70R16 size, our calculation would confirm that the size would result in a section height of 6.20", approximately a 1.8-inch taller sidewall.


    Last edited by Franklin; 04-18-2005 at 01:18 PM.

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