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wheel idiot needs explanation of backspacing please

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 77Jimmy, Jun 23, 2003.

  1. 77Jimmy

    77Jimmy 1/2 ton status

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    Let's play educate the idiot...what is backspacing? /forums/images/graemlins/blush.gif how do you measure it? etc.

    I'm looking to replace my existing rims on a D44 & 12b w/ 15x8 wheels & 33x10.5 tires. I think I need the 3 5/8 backspaced rim??? I currently have 15x8.5 wheels and 31x10.5 tires.
     
  2. Confedneck

    Confedneck 3/4 ton status

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    take the rim, just the rim, lay it face down on the ground, run a straight edge from one side of the wheel to the other..then use a ruler to measure from where the wheel rests against the hub, the flat part, to the ruler, that's your backspacing... help any?
     
  3. chebywanna

    chebywanna 1/2 ton status

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    face down or dirty side down? and then measure from ground to where the rim would be touching the hub. i thoght it was dirty side down. /forums/images/graemlins/confused.gif
     
  4. wrathORC

    wrathORC 1/2 ton status

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    On the backside of the wheel lay a piece of something flat. You measure from the wheel mating surface to that. This is backspacing. Some companies measure from the wheel mating surface to where the bead rides on the tire. Usually there is no more than a 1/4" difference so it's not a big deal.

    Offset is measured from the wheel centerline to the wheel mating surface. You have negative offset when the wheel mating surface is closer to the brake side of the wheel than the outside of the wheel.

    For example, a 15x10 wheel with 4" of backspacing would have a 1" negative offset.
     
  5. TXsizeK5

    TXsizeK5 1/2 ton status

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    [ QUOTE ]
    On the backside of the wheel lay a piece of something flat. You measure from the wheel mating surface to that. This is backspacing. Some companies measure from the wheel mating surface to where the bead rides on the tire. Usually there is no more than a 1/4" difference so it's not a big deal.

    Offset is measured from the wheel centerline to the wheel mating surface. You have negative offset when the wheel mating surface is closer to the brake side of the wheel than the outside of the wheel.

    For example, a 15x10 wheel with 4" of backspacing would have a 1" negative offset.

    [/ QUOTE ]

    Yea this is right... another example would be a 15x12 wheel with 4" of backspacing would have negative 2" offset.
    You always get the width of the wheel and find half of it. And backspacing is how far the vertical part of the wheel is in relation to the center getting closer to the outside and offset is the vertical part of the wheel in relation to the center getting closer to the inside.

    Ie. Set the wheel vertical so that you can roll it. Find the very center and if you have 4" of backspace that means the vertical part of the wheel (the wall or whever your lugnuts go into) will be 4 inches to the middle from the outside of the wheel. It will be 6 inches from the inside of the wheel to the center making it negative 1" offset. Becusae if you have positive offset, then the vertical part of the wheel gets closer to the inside therefore pushing the round part of the wheel (where the tire actaully sits on) out further giving you the gangsta low rida' look.
    Hope this helps.
     
  6. rawhead

    rawhead Registered Member

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    Check this page out. It helps explain it a litle better.
    web page
     
  7. 77Jimmy

    77Jimmy 1/2 ton status

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    Thanks to all...that helped a bunch. /forums/images/graemlins/thumb.gif
     

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