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Silverdo 2008 Rim size info ???

Discussion in 'Chevy Trucks' started by scottL, May 14, 2009.

  1. scottL

    scottL PlowSite.com Addict
    Messages: 1,600

    Hey guys,

    Need some info..... I have a 2008 Silverado 2500 HD crew/long bed currently with the 16" rims ( 245/75-16 ).

    I want to upgrade and go with 18" rims but I am confused on what sizes I have to pay attiention to. I already suspect I'll have to take it somewhere for the speed calibration ( probably just the dealer I guess )

    Offset: ????
    Back Spacing: ????
    Bolt Pattern: I believe it is 8-165 or also written as 8-65

  2. William B.

    William B. Senior Member
    from S.E. IA
    Messages: 978

    Offset and backspacing I can't help you on but you want the 8x 6.5 bolt pattern. How wide of rim also is important when it comes to offset and backspacing as well.
  3. scottL

    scottL PlowSite.com Addict
    Messages: 1,600

    There is lies my problem. I'm not sure where I'm at and exactly what I want per sae. I do want an 18" rim for the goal of a better appearance and taller profile. I believe my total wheel diameter right now is 30.5" I do not want to go more than 32.5". What that would equate in width ... dunno - looking for insight.

    The local stores haven't a clue.
  4. JD Dave

    JD Dave PlowSite Fanatic
    Messages: 11,032

  5. scottL

    scottL PlowSite.com Addict
    Messages: 1,600

  6. Q101ATFD

    Q101ATFD Senior Member
    Messages: 277

    GM no longer will calibrate your speedometer for a tire/wheel package that was not an option for that truck from the factory. The only two options on a 2007+ HD are LT245/75R16 on a 16" and LT265/70R17 on a 17" wheel. If you want the speedometer to be correct, you'll have to buy a programmer, or make friends with somebody who has one. However, GM will not honor the drivetrain warranty with *either* aftermarket tires/wheels, or a non-GM ECM flash (e.g. speedo reprogram).

    If it were me (it is, but with different size tires), I would keep the factory tires and wheels in your garage, and put them on if you have to take the truck in for drivetrain work. They don't care whats on it for oil changes, etc. I would also keep the speedo the same and just remember that your speed is always going to be whatever percentage faster than is displayed. The Duramax/Allison package is way to expensive to void the 100k warranty on.
  7. Q101ATFD

    Q101ATFD Senior Member
    Messages: 277

    Also, you're two most common tire sizes on 18" rims for these trucks are going to be LT265/65R18 and LT285/65R18. I would shoot for a width of 8" to 9" - that will allow both of the mentioned tires to fit to spec.
  8. scottL

    scottL PlowSite.com Addict
    Messages: 1,600

    Thanks Guys!

    The on website was also a great deal of help in finding the offset and backspacing. This helped a ton in finding rims and understanding what size difference the over all wheel would end up to be along with anticipated speed differences.

    I'll check with my local GM folks ( if they are still around :cry: ) and validate the warranty. Don't want to void a warranty. I've already had the trans rebuilt and it's just shy of two seasons :cry: