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Tire size question

Discussion in 'Intermediate CJ-5/6/7/8' started by SwampRatt, Sep 22, 2006.

  1. Sep 22, 2006
    SwampRatt

    SwampRatt 1973 CJ-5

    Naperville, Illinois
    Joined:
    Sep 15, 2006
    Messages:
    109
    I'm a newbie here and to Jeeps and I have a question. I need to
    Replace a tire as the spare has rotted.

    I see posts here and other places referring to their tires as 31s or 33s etc.
    I saw another port referring to a tire size of 33 x 10.5.
    My tires are LT 325 MT 325/60 R15 106Q MS.

    I take this to be:
    LT – I don’t know what this means, something Terrain?
    325 mm wide tire
    The height is 60% of the width
    Radial
    For a 15 inch rim.
    Mud and Snow

    I measured the diameter of the tire and it’s roughly 31 inches. Is this what everyone is referring to as a 31?

    Thanks in advance.
    SwampRatt
     
    SwampRatt, Sep 22, 2006
    #1
  2. Sep 22, 2006
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Aug 10, 2003
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    23,596
    timgr, Sep 22, 2006
    #2
  3. Sep 22, 2006
    sparky

    sparky Sandgroper Staff Member Founder

    Perth, WA
    Joined:
    Sep 20, 2002
    Messages:
    9,221
    There's no 325/60 R15 listed there Tim, not that I saw?

    A 325/60 R15 probably is close to 31" but it's not a 31" tire as in 31x10.50. That's a flotation tire size denotation. The 325.... is a metric tire size. Just a different way of measuring tire size.
     
    sparky, Sep 22, 2006
    #3
  4. Sep 22, 2006
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Yeah, I read 235, not 325.

    Using the formula on the page ((325/25.4)*0.6*2) + 15) = 30.4", pretty close to 31".

    325 is in mm, with 25.4mm/in. 60% aspect ratio, top and bottom, with a 15" wheel.
     
    timgr, Sep 22, 2006
    #4
  5. Sep 22, 2006
    BlueFlu

    BlueFlu past owner of some ecj5's

    Hermitage, TN
    Joined:
    Jan 21, 2004
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    1,552
    Thought M&S meant Mostly Stuck? :?
     
    BlueFlu, Sep 22, 2006
    #5
  6. Sep 22, 2006
    SwampRatt

    SwampRatt 1973 CJ-5

    Naperville, Illinois
    Joined:
    Sep 15, 2006
    Messages:
    109
    Interesting, thanks for the information.
    So when somebody is sticking on “33s” that’s a flotation tire?
    How is a flotation tire measured?
     
    SwampRatt, Sep 22, 2006
    #6
  7. Sep 22, 2006
    sparky

    sparky Sandgroper Staff Member Founder

    Perth, WA
    Joined:
    Sep 20, 2002
    Messages:
    9,221
    There's different ways to measure tire sizes. Guess I wasn't clear. This link explains it much better than I did.
    http://www.yokohamatire.com/utsizesys.asp

    33 what? I have 33x10.5 on my Jeep, I replaced the 33x12.5s that were on it previously.
     
    sparky, Sep 22, 2006
    #7
  8. Sep 22, 2006
    SwampRatt

    SwampRatt 1973 CJ-5

    Naperville, Illinois
    Joined:
    Sep 15, 2006
    Messages:
    109
    So this (in flotation speak) is 31 in diameter and 15.5 in wide?

    Sorry if I appear dense, I've much to learn.
     
    SwampRatt, Sep 22, 2006
    #8
  9. Sep 22, 2006
    sparky

    sparky Sandgroper Staff Member Founder

    Perth, WA
    Joined:
    Sep 20, 2002
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    9,221
    Yes, did you read the link I posted above? It does a MUCH better job of explaining than I did. :)
     
    sparky, Sep 22, 2006
    #9
  10. Sep 22, 2006
    SwampRatt

    SwampRatt 1973 CJ-5

    Naperville, Illinois
    Joined:
    Sep 15, 2006
    Messages:
    109
    Yes. Thanks for the help!
     
    SwampRatt, Sep 22, 2006
    #10
  11. Sep 22, 2006
    jd7

    jd7 Sponsor

    Nacogdoches,Texas
    Joined:
    Mar 30, 2004
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    1,745
    I've had two sets of tires that were 325/60- 15 it's nothing but a 12.50/31-15 It came out a few years back BF Goodrich had it in a T/A which was the first set I had. Was marketed for unlifted Jeeps as I recall. I have a set mounted on 10" wheels that are Super Swamper SSR's I really like them. Sling the mud and clean pretty well. You can hear them pretty well growling on the road once you get up to speed, but that's fine.
     
    jd7, Sep 22, 2006
    #11
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