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Discussion Starter #1 (Edited)
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 vehicle's 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 backward 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.



***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.


I hope this helps.

For more technical information visit the Tips & Guides Section at DiscountTire.com
 

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I'm probably thinking about this too hard, but I just wanted to try and get something straight in my head, because honestly, I've had questions about how to figure this stuff out.

If I have a positive offset (say +15 millimeters), then the wheel will be CLOSER to the suspension than a zero offset wheel and look "sucked in." And if I have a negative offset (-15 millimeters), then the wheel will be FARTHER from the suspension, and look like it's sticking out, correct?
 

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Discussion Starter #4
I'm probably thinking about this too hard, but I just wanted to try and get something straight in my head, because honestly, I've had questions about how to figure this stuff out.

If I have a positive offset (say +15 millimeters), then the wheel will be CLOSER to the suspension than a zero offset wheel and look "sucked in." And if I have a negative offset (-15 millimeters), then the wheel will be FARTHER from the suspension, and look like it's sticking out, correct?
It all depends on the rim width but typically speaking, yes.
 

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Now also keep in mind that a +15 offset on let's say a 9" wide wheel for example, will not looked sucked in on every vehicle especially the Tundra. Every vehicle has different offset ranges depending on the look wanted or suspension set-up.
Oh, I understand that. I only said that to help get a picture of it in my head.
 
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discount tire....can i install raceline rampage 20x9" +30 w/a 305-55-20 0r 305-50-20 with out any serious rubbing .......i have a 2'' coilover already installed in front .....looks like it would get purty close to the upper control arm.....but maybe not. yer thoughts ?

thanks for any input....
 

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Discussion Starter #9
discount tire....can i install raceline rampage 20x9" +30 w/a 305-55-20 0r 305-50-20 with out any serious rubbing .......i have a 2'' coilover already installed in front .....looks like it would get purty close to the upper control arm.....but maybe not. yer thoughts ?

thanks for any input....
What year Tundra do you have?
 

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So when a lift kit manufacture recomends backspacing, are they saying min or max? For example when they say a 305/55R20 will fit on a 20x9 w/ 6" bs, will a wheel with 5.5 or less still be okay? Thanks.
 

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Discussion Starter #13
So when a lift kit manufacture recomends backspacing, are they saying min or max? For example when they say a 305/55R20 will fit on a 20x9 w/ 6" bs, will a wheel with 5.5 or less still be okay? Thanks.
Lift kit manufacturers usually state a max backspace (highest backspace recommended).

If the lift kit manufacturer states a 305/55R20 will fit with a 20x9 with a 6" backspace, a wheel with any less BS will also work. A lower backspace will move the wheel and tire assembly out, away from the suspension and frame.
 

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Have a question for discount tire as well. I have a 2010 stock height double cab. Would it do any running at all with a set of cranks at 0 offset with 275/60/20 tires? Been trying to figure this out for a while now. Thanks
 

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Discussion Starter #15
Have a question for discount tire as well. I have a 2010 stock height double cab. Would it do any running at all with a set of cranks at 0 offset with 275/60/20 tires? Been trying to figure this out for a while now. Thanks
It shouldn't. You'd run into issues if you decide to go with a larger tire in the future though. (without a lift that is.)
 

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Thanks!
 

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Discount Tire,
I found a set of wheels and tires on discounttiredirect.com that I was wanting to purchase and saw that it said free shipping which I thought was even better! However whenever I went to the checkout page my total went from $1600 to $2500 because of shipping costs. So I went to your page and it says you offer free shipping to the lower 48 states & Canada. Curious as to why Canada is offered free shipping and Alaska is charged $950 for shipping when Canada is just as far north as we are? Is there anyway to bypass this?
 
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Discussion Starter #19
Discount Tire,
I found a set of wheels and tires on discounttiredirect.com that I was wanting to purchase and saw that it said free shipping which I thought was even better! However whenever I went to the checkout page my total went from $1600 to $2500 because of shipping costs. So I went to your page and it says you offer free shipping to the lower 48 states & Canada. Curious as to why Canada is offered free shipping and Alaska is charged $950 for shipping when Canada is just as far north as we are? Is there anyway to bypass this?
The only thing I can think of would be to have the product shipped somewhere in Canada and them pick them up there. Canadian Shipping is FREE but we do collect their Duties, Taxes, Customs Fees and Brokerage. This still costs a decent amount but it would save you a few hundred dollars.

Shipping to Alaska is just plain expensive. I with there was a cheaper way to get the product there but there just isn't.
 

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I also have a question about backspacing. Im looking at Xd addicts and they offer them in +18 offset. But they offer them in two different backspacing 5.71 and 4.53. Which one should I go with? I have a 3 inch spacer lift. Thanks
 
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