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Offset and backspace

Discussion in 'Wheels & Tires' started by Sean266, Feb 1, 2014.

  1. Feb 1, 2014 at 7:50 PM
    #1
    Sean266

    Sean266 [OP] #ThinBlueLine Staff Member

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    I took this info off of another board, as I figured we could benefit from it here, on Tundras.com.

    Offset and backspace are essentially two different ways of looking at the same thing. They determine the location of the wheel and tire assembly when bolted to the vehicles hub. (how far in - tucked, or how far out they will sit)

    Offset is the measured distance between the hub mounting surface and the wheels center line.

    With X being the determined offset, the hub mounting surface on positive offset wheels is X amount forward from the wheel center line. The hub mounting surface on negative offset wheels is X amount backwards from the wheel center line. The hub mounting surface on 0 offset wheels is the wheel center line. ​

    Backspacing is the measurement from the hub mounting surface to the back edge of the wheel.


    [​IMG]

    ***Typically speaking, the higher the offset/backspace, the more the wheel will tuck inwards towards the suspension or away from the fender. The lower the offset/backspace, the more the wheel will push out away from the suspension or towards the fender.

    For Example:

    *If the offset on a 9" wide wheel is +12mm, the hub mounting surface will be 12mm forward from the wheels center line. Measuring from the hub mounting surface to the back edge of the wheel, the backspacing is 5.5"

    *If the offset on a 9" wide wheel is -12mm, the hub mounting surface would be 12mm towards the back of the wheel from the wheels center line. Measuring from the hub mounting surface to the back edge of the wheel, the backspacing is 4.5" ​


    Here's how to calculate the backspacing using the rim width and offset:

    First - add 1" to the rim width and then divide by 2 to find the wheels center line (you have to account for the wheel flange which is why you add 1" to the rim width) . Second - convert the offset which is in millimeters into inches. There is 25.4mm in 1 inch so divide the offset by 25.4. Lastly - add the converted offset to the wheels center line if the offset is positive for the correct backspacing. Subtract the converted offset to the wheels center line if the offset is negative for the correct backspacing.

    For Example:

    17x9 +12mm offset

    *9" rim width + 1" = 10"
    *10"/2 = 5" (wheels center line)
    *+12mm offset/25.4 = 0.47" (0.50" rounded up)
    *0.50" + 5" = 5.50" Backspace


    17x9 -12mm offset

    *9" rim width + 1" = 10"
    *10"/2 = 5" (wheels center line)
    *-12mm offset/25.4 = 0.47" (0.50" rounded up)
    *0.50" - 5" = 4.50" Backspace​


    ***Please note that the wheels center line is the backspacing for 0 offset wheels.
     
    TruckyTruck likes this.
  2. Feb 4, 2014 at 8:40 AM
    #2
    TruckyTruck

    TruckyTruck New Member

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    good info. thanks!!!
     
  3. Apr 22, 2014 at 2:24 PM
    #3
    mike.D1Esel

    mike.D1Esel SSG Badass

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    Sticky this please!
     
  4. Apr 22, 2014 at 2:48 PM
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    jberry813

    jberry813 The Mad Scientist

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  5. Apr 22, 2014 at 6:04 PM
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    Bob

    Bob Member Staff Member

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    Done!
     
  6. Apr 22, 2014 at 6:59 PM
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    mike.D1Esel

    mike.D1Esel SSG Badass

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    appreciate it!!!
     
  7. Sep 2, 2014 at 9:52 AM
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    jedi926

    jedi926 New Member

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    Hello. Brand new to the site. I am trying to find an all black alloy wheel that I can put on my stock 2013 Tundra DC 4x4. I am looking to do a RL 3/2 I am struggling to find the right wheel with the proper backspace and offset. I believe the tire I am thinking about purchasing is the Nitto 305/70R17. My third Toyota truck and my first attempt at a lift and aftermarket wheels. I definitely do not want anything rubbing against the UCA. Can you guys help me out? Thanks in advance. Jedi.
     
  8. Jan 20, 2015 at 6:58 PM
    #8
    MrTuRDPro

    MrTuRDPro New Member

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    None...yet!
    Seems like this is the place to post this great little resource. If you're interested in seeing how your stock tires match up to other sizes you may be considering for upgrade, this calculator is amazing. It provides a detailed comparison of tire sizes in the following areas:

    Tire specs:
    - Diameter
    - Width
    - Sidewall
    - Circumference
    - Revs/Mile

    Speed Differences at 20 - 90 MPH (in 10 MPH increments)

    Dang, this tool even gives you a "Visualizer" button which allows you to see both tires side by side, across two separate views (straight on, and the side view). It's been a crucial tool for me and I really hope it proves valuable for everyone else. Make sure to click the "Tire Size Comparison" tab in the middle window pane of the page...everything beyond that is very intuitive. Here's the site:

    http://tire-size-conversion.com/tire-size-calculator/

    Enjoy!
     
  9. Jan 22, 2015 at 6:41 PM
    #9
    Tundra2010

    Tundra2010 New Member

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    So just to be clear, which will make the wheel stick out further negative or positive?
     
  10. Jan 22, 2015 at 8:40 PM
    #10
    Relentless

    Relentless Tundra newb Vendor

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    Just a few, more to come
    Negative offset sticks the wheel/tire out
     
  11. Feb 11, 2015 at 2:46 PM
    #11
    Mkyle

    Mkyle New Member

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    Hey just joined today I have a question I just ordered a set of 18x9 xd hoss wheels with 35" 12.50 toyo mt tires the offset is +30 will this fit I just noticed the uca may be in the way I am also installing a 3" low range off rd leveling kit
     
    Last edited: Feb 11, 2015
  12. Feb 12, 2015 at 3:52 PM
    #12
    tat2ude39

    tat2ude39 MYota

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  13. Feb 12, 2015 at 5:12 PM
    #13
    Mkyle

    Mkyle New Member

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    Thanks from what that says it should wrk I'll find out in a couple days
     
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