Offset & Backspace - How Do They Relate? - Page 2 - Toyota FJ Cruiser Forum
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post #11 of 20 (permalink) Old 05-31-2013, 10:40 AM Thread Starter
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Re: Offset & Backspace - How Do They Relate?

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Last edited by Discount Tire; 09-19-2013 at 11:50 AM.
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post #12 of 20 (permalink) Old 09-19-2013, 11:31 AM
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Re: Offset & Backspace - How Do They Relate?

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Discount Tire previously said: View Post
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.

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

-Matt
This is a great old sticky. I believe in the second example, the equation should read 5" - 0.50" = 4.50" Backspace.

In any case, this really helps us understand backspacing and offset. Thanks!
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post #13 of 20 (permalink) Old 09-19-2013, 11:53 AM Thread Starter
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Re: Offset & Backspace - How Do They Relate?

Good catch ksfrogman. Edit made!

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post #14 of 20 (permalink) Old 10-30-2013, 08:02 AM
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Re: Offset & Backspace - How Do They Relate?

Matt isn't a 4.5 backspace in general what most FJ Cruisers will need with aftermarket tires/rims?

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post #15 of 20 (permalink) Old 10-30-2013, 03:19 PM Thread Starter
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Re: Offset & Backspace - How Do They Relate?

Yes, generally speaking, wheels with a 4.5" backspace are great for most FJ applications.

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post #16 of 20 (permalink) Old 06-15-2014, 10:12 AM
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Re: Offset & Backspace - How Do They Relate?

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Yes, generally speaking, wheels with a 4.5" backspace are great for most FJ applications.
Wheel spacers seem to be very popular. Is it possible and/or recommended to use wheel offset rather than wheel spacers? It seems simpler that way.
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post #17 of 20 (permalink) Old 06-15-2014, 12:12 PM
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Re: Offset & Backspace - How Do They Relate?

Click on that Discount Tire link on the Section heading. Then click on the "Info" section in the Discount Tire website. Some good info in there. And thanks Discount Tire for the info!
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post #18 of 20 (permalink) Old 07-25-2014, 09:59 PM
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Re: Offset & Backspace - How Do They Relate?

What is the back space on stock 16" TRD wheels? Would it be more than 4.5"?
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post #19 of 20 (permalink) Old 07-26-2014, 10:01 AM Thread Starter
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Re: Offset & Backspace - How Do They Relate?

Quote:
Maxx previously said: View Post
What is the back space on stock 16" TRD wheels? Would it be more than 4.5"?
The factory 16" wheels are 7.5" wide with a +15mm offset which equals 4.85" backspacing.

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post #20 of 20 (permalink) Old 08-18-2015, 01:55 PM
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Re: Offset & Backspace - How Do They Relate?

Nevermind, I found it.

Last edited by All.We'll.Drive; 08-18-2015 at 01:58 PM.
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