1. Welcome To GMTruckClub.com!

    The #1 Chevy Truck Forum Online
    Online since 2004, we are the #1 Chevy Truck & SUV forum and user community. If you have any questions about your Chevy or GMC Truck, SUV or Crossover, or just want to connect with other GM owners and enthusiasts around the world, you've found the best place on the internet to do that.

    Join Today ~ It's Free
    Registering is Free and Easy! Hope to see you on the forums soon!

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

Discussion in 'Wheels & Tires' started by Springthing, Apr 7, 2009.

  1. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    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?
  2. pmf608

    pmf608 Epic Member 5+ Years 1000 Posts

    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: Apr 7, 2009
  3. Mindi51982

    Mindi51982 Rockstar 100 Posts

    Go back to school :lol::great:
  4. CarpenterGuy

    CarpenterGuy Epic Member 5+ Years 500 Posts

    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.
  5. Pete95Sierra

    Pete95Sierra Epic Member 5+ Years ROTM Winner 1000 Posts

    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
  6. 95CTburb19

    95CTburb19 Epic Member 5+ Years 1000 Posts

    285's should be fine :great: Throw the 305's on craigslist, I bet they'll sell pretty quickly.
  7. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    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

Share This Page