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4.5" Backspacing for 1975 Blazer

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by CooknwithGas, Jan 11, 2002.

  1. CooknwithGas

    CooknwithGas 1/2 ton status

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    4.5\" Backspacing for 1975 Blazer

    I am close to purchasing wheels for my 1975 blazer and am interested in Rock Crawlers. I'm not sure what Backspacing is, but I was told I need 4.5" backspacing for my rig.

    Does anyone have Rock Crawlers with 4.5" backspacing installed on a Blazer and do you have pictures?

    Second question - is 8" width a good choice for Rock Crawlers on a blazer? I plan on installing 33" tires.

    Any help would be appreciated.

    Scott.


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    "It's better than a sharp stick in the eye."
     
  2. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Re: 4.5\" Backspacing for 1975 Blazer

    My personal recommendation would be 3.5" if you are running 6 lug axles. The 4.5" spacing might actually make contact with the tie rod ends, but I don't know for sure.

    8" wide rims should be fine for 33" tires if they are no wider than a 12.50".
     
  3. RedDwarf

    RedDwarf 1/2 ton status

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    Re: 4.5\" Backspacing for 1975 Blazer

    Backspacing is the distance from the inner edge of the wheel to the mounting surface that buts up against the hub.

    I have a hair over 4" of backspacing on my 15x10"s. I clear the tie rod ends by about 1/8". So no, you don't want 4.5" backspacing, especially on a wheel as narrow as 8". Call somewhere else and order soem 8"s with 3 5/8" backspacing. Any more than that on an 8" rim will stick the tires waaaay up under the fenders.

    <P ID="edit"><FONT class="small">Edited by RedDwarf on 01/11/02 10:27 AM.</FONT></P>
     
  4. RedDwarf

    RedDwarf 1/2 ton status

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    Re: 4.5\" Backspacing for 1975 Blazer

    Oh, and 8" is fine for a 33x12.50" tire.
     
  5. CooknwithGas

    CooknwithGas 1/2 ton status

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    Re: 4.5\" Backspacing for 1975 Blazer

    Red:

    Do you have a picture of your rims on your truck?

    Thanks.

    ______________

    "It's better than a sharp stick in the eye."
     
  6. CooknwithGas

    CooknwithGas 1/2 ton status

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    Re: 4.5\" Backspacing for 1975 Blazer

    I did some research and found out a few things if anyone is interested. It seems there is some confusion between OFFSET and BACKSPACING. I found a clear definition of the difference as follows:

    "Backspacing is the distance from the rear edge of the rim to the mounting surface. Offset is the distance from the rear mounting surface to the center of the rim. An 8" rim with 4" backspacing has 0" offset. A 10 " rim with the same backspacing has a + 1" offset. An 8" rim with +4" offset has 0" backspacing. "

    According to Discount Tire, a 1975 Chevy Blazer should have 4.5" backspacing which would be the same as -1/2" offset on an 8" rim. 13mm is the same as 1/2"

    I hope this helps anyone who had the same question.

    Scott.

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  7. RaisedK5

    RaisedK5 1/2 ton status

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    Re: 4.5

    UUMMMMM, I think they are wrong, I don't think you'll be able to it 4.5 inch backspaced wheels on a 1/2 ton chevy, (blazer) . I used to have 3 5/8 backspacing on my 15x10s and had less than a 1/2 inch clearance to the tie rod, but if you want to be sure pull off one of your wheels and measure how much clearance you have. And just for point of reference, my truck came with 15x7s originally, with 0 offset which equates to a 3.5" backspace. I think there may be a typo in Discounts fitment chart. Just my.02. [​IMG]

    Leland aka RaisedK5

    "The Voices told me to do it!"
    <a target="_blank" href=http://www.coloradok5.com/gallery/albun91>This is what they told me to do</a>
     
  8. CooknwithGas

    CooknwithGas 1/2 ton status

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    Re: 4.5

    Thanks Leland:

    I'll double check that. I don't want them to stick in too far. Your truck looks great by the way. Those are some big tires!

    Scott.

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  9. RaisedK5

    RaisedK5 1/2 ton status

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    Re: 4.5

    Thanks for the compliment[​IMG].

    Those tires don't look quite as big as they used to now that i've opened up the front fenders, but ya they get the job done.


    Leland aka RaisedK5

    "The Voices told me to do it!"
    <a target="_blank" href=http://www.coloradok5.com/gallery/albun91>This is what they told me to do</a>
     
  10. K5Jimmy

    K5Jimmy 1/2 ton status

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    Re: 4.5\" Backspacing for 1975 Blazer

    Stock backspacing for a 75 6 lug is 3 5/8".....4" of backspacing will Probably hit your tie rod end on the passenger side (some guys on this site run 4" and report no trouble at all)......on a 6 lug, 4" is the absolute maximum backspacing ...offset is a byproduct of backspacing....an 8" wheel is fine for 12.5 width, although some folks prefer 10" for looks.......with the same backspacing, a 10" wheel will stick out further than an 8".......I run 10" Rally's with 33's and 4" of backspacing, and since I have interference with my tie rod passenger side, I run an old Crager 3/8 spacer (pn29200) for clearance.....for daily use, I run the stock 8" Rally with 33 AT's.....the 10" Rally's with BFG Muds are for play........hope this helps...JD


    Stuck?...Hell no..I still got some gas left..
     
  11. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    Re: 4.5\" Backspacing for 1975 Blazer

    I have 4.25" backspacing on 16x10 Wheels. Perfect for my 91.

    No rubbing on suspension/steering but I have x over if that makes any difference.

    Dave

    Rehab is for quitters.
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