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  1. #1
    Legend

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    Default Is my math correct? This tire size MINUS an inch...?

    I am trying to get from one tire size to get an inch thinner tire. Please tell me if I have the math correct:

    305 70 16 is what I have on. I want to get an thinner tire because of some slight fender rub. Please tell me if I have this correct:


    305 70 16 = 33 x 12.01 x 16

    12.01 - 1 = 11.01

    33 x 11.1 x 16 = 285 75 16 (actually 280 77 16)


    So putting a 285 75 16 tire on my 10 inch rims should decrease the width of the tires by 1 inch, correct?


    Anyone?



    Bonus question: I should be able to go one inch thinner still with a 16 x 10 rim, right? Will that give me too thin a look?
    Steven



    "The Sarge"
    1999 Chevy Suburban LT- K2500
    7.4 454 Vortec, 4WD
    305/70/16 on Eagle Alloy




  2. #2

    Default

    Yes, this is as close to one inch as you will get. The only numbers you need to look at for width are the first series - 305 and 285. These are in millimeters, and each inch is 25.4 millimeters. A 20mm decrease is a bit over 3/4 of an inch. going down to a 275 would be slightly over an inch. Long story short. Your calculation was one of the 2 closest sizes. You should be able to stick with the 10 inch rim, without looking too narrow. hope this helps
    Last edited by pmf608; 04-07-2009 at 07:15 PM.

    2008 FORD F350. My new all-around truck.
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  3. #3

    Default

    Go back to school
    Mindi
    1998 1500 Silverado Z71
    2006 YFZ450

  4. #4
    Master Mechanic CarpenterGuy's Avatar
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    Default

    a kid at my school has 285/75/16's. his are thinner than my old trucks 33x12.5's. i'm sure it'll work for you.
    2006 Silverado Z71 - 97,000 - totaled, RIP
    2006 Silverado Z71 - 122,000 (K&N 77 Series CAI, PowerAid TBS, Magnaflow dual rear exit, 33x12.50 Mickey Thompson MTZ, Tuff Country Torsion Keys, Tuff Country Add-A-Leafs)
    1966 C10 swb stepside (Gen I 350, Turbo 400 trans, dual cyl power brakes, front discs)
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  5. #5

    Default

    it will work fine. the 285 tires are usually more like 11.5 inches wide and on the 10" wide rim they will look good. If you want to see what a 285 looks liek ona 16x8 rim look at my pics, that is the setup I ran
    PETE
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  6. #6

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    285's should be fine Throw the 305's on craigslist, I bet they'll sell pretty quickly.
    Dan
    1999 GMC Sierra 2500 350 vortec
    1967 Jeep M725 ambulance 230 tornado
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  7. #7
    Legend

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    Default

    Thanks for all the input. That's what I'll do then.

    Mindi- unfortunately they didn't teach tire size mathematics in my school! lol

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