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Great diagram of Wheel Backspacing and Other Measurements

Discussion in 'Wheels & Tires' started by bry2500, Feb 24, 2009.

  1. bry2500

    bry2500 New Member

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    Wheel Backspacing and Offset

    Before mounting a set of aftermarket wheels, there are some dynamics involved with fitment that are best to understand first.
    1. Wheel Diameter. This is the diameter of the wheel. Stock wheels are commonly 15 or 16 inch diameter. This dimension is usually in 1 increments (i.e. 15, 16, 17) but some manufacturers offer 16.5, which is rare.
    2. Wheel Width. This is the width of the wheel, measured inside the outer lip of the wheel. This dimension is usually in 1/2 increments (i.e. 7.5, 8)
    3. Wheel Center. This is the center of the wheel in relation to the width.
    4. Offset. The distance from the centerline of the wheel to the face of the mounting surface of the wheel that contacts the hub.​
    4.1 Zero Offset. Indicates the mounting surface is at the wheel center.
    4.2. Negative Offset. Indicates the mounting surface is behind (or inboard) the centerline of the rim. This is often found on standard rear-wheel-drive vehicles and on so-called reversed rims. (Diagram below shows negative offset)
    4.3 Positive Offset. Indicates the mounting surface is in front of (or outboard) the centerline of the rim. This is often found on front-wheel-drive vehicles. Stock Tacoma wheels have Positive offset.​
    5. Backspacing. The distance from the mounting surface to the inside lip of the wheel. This measurement is closely related to offset (without actually measuring, backspacing is about equal to [Wheel Width / 2] + [Offset] + [about 1/4] ).
    6. Centerbore. The centerbore of a wheel is the size of the machined hole on the back of the wheel that centers the wheel properly on the hub of the car. This hole is machined to exactly match the hub so the wheels are precisely positioned, minimizing the chance of a vibration. This measurement may be critical to clear the hubs of a 4WD.
    7. Bolt Circle. Also known as PCD (Pattern Circle Diameter). The bolt circle represents the diameter of an imaginary circle that goes through the center of the bolt holes. 4x2 Tacoma Bolt Circle: 5 lug on 4.5 PCD; 4x4/Prerunner Tacoma Bolt Circle: 6 lug on 5.5 PCD.​
    [​IMG]
    (Diagram: Alloy Wheel Cross-Section)
    #1
    1 person likes this.
  2. johnsstart

    johnsstart New Member

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    Well thats was def informative thanks learn something new every day :great:
    #2
  3. Pete95Sierra

    Pete95Sierra New Member

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    great diagram this will help a lot of people. stickied :great::great:
    #3
  4. bry2500

    bry2500 New Member

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    Hey if I didn't find it I'm sure someone else would have.

    Glad I could help anyone.
    #4
  5. TRPLXL2

    TRPLXL2 New Member

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    WOW! That is an awesome write up, I printed this off and gave it to my boyfriend who thinks he knows it all when it comes to this kind of stuff. Thanks very much, this will have a special place on the garage wall right next to the picture of my truck. :lol:
    #5
  6. dwill3015

    dwill3015 New Member

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  7. shurshot

    shurshot New Member

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    Good information since I am currently looking at 20" wheels for my 2009 GMC!! Thanks!
    #7
  8. countryboy73703

    countryboy73703 New Member

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    well that cleared up some muddy water...
    #8
  9. ippielb

    ippielb New Member

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    The diagram is what really did it for me. Thanks.
    #9
  10. larryleeUSN

    larryleeUSN New Member

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    does any one know?

    does anyone know the stock offsetting and back spacing of the stock 06 silverado rims? not the Z-71 rims the bullit hole style rims?
    #10
  11. jerseymike68

    jerseymike68 New Member

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    great sources here
    #11
  12. kbuss

    kbuss New Member

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    im still a bit confused. im looking at some wheels right now and they say they have an offset of 15mm. does offset have anything to do with how far the wheel and tire will stick outside the wheel well---and if so would a negative offset stick out further or less? if someone could please help me that would be great, thanks.
    #12
  13. chevyman2004

    chevyman2004 New Member

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    negative offset the wheels will stickout farther and positive offset the wheels will be further in. Hope that helps.
    #13
  14. jerseymike68

    jerseymike68 New Member

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    nice instructions
    #14
  15. ahm1127

    ahm1127 New Member

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    This was very help full, thanks.
    #15
  16. 1995z71

    1995z71 New Member

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    that is going to help me alot, i was geting ready to buy some new rims. thanks
    #16
  17. ChevyFan

    ChevyFan Administrator Staff Member

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    Great diagram, let's get more of this type of thing up here. :great:
    #17
  18. Joethepoolguy

    Joethepoolguy New Member

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    :great:Thank you for that information!!! I am thinking about buying new wheels sometime this summer and now I know how to figure out the back-spacing. The wheels I am thinking about are the ATX Artillery.Anyone have these on their truck, so I can see what they look like? The viewer on TireRack only helps a little.
    #18
  19. smiller09

    smiller09 New Member

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    Nice write up will help a lot of people looking for new rims.
    #19
  20. cmestax

    cmestax New Member

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    Great Info!
    #20

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