Stock wheels are not 6.25 backspace. Math say its 5.5" - Jeep Wrangler Forum
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Old 12-01-2017, 12:20 PM
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Stock wheels are not 6.25 backspace. Math say its 5.5"

Everywhere I read people keep posting that the backspace on stock wheels is 6.25". Is that for TJ rims?

This is for 2017 stock rubicon wheels (187.5). They're stamped +44.45mm offset so the math for backspace says different, if Im doing it correctly.

7.5" = 190.5mm
190.5mm 2 = 95.25mm
95.25mm + offset (44.45mm) = total backspace of 5.5"

Correct?




Reason for doing all this figuring is Im installing a 3.5 gamechager lift. Metalcloak recommends 2" spacers to run 35" tires. I plan to run 285/75/17 which are 1.3" difference in width from typical 35" tires. Essentially I can run the smallest spacer (1.25") with these tires and still maintain less than 5.5" backspacing MC requires to clear the new rear swaybar links? Want to run smallest spacers possible to keep tires inside the wheelwell.

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Old 12-01-2017, 12:24 PM   #2
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No jk stock rims are 6.25

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Old 12-01-2017, 12:49 PM   #3
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Quote:
Originally Posted by RoosterCon View Post

This is for 2017 stock rubicon wheels (187.5). They're stamped +44.45mm offset so the math for backspace says different, if Im doing it correctly.

7.5" = 190.5mm
190.5mm 2 = 95.25mm
95.25mm + offset (44.45mm) = total backspace of 5.5"

Correct?
Rubicon wheels are 17", not 18". They are 7.5" wide. Are you sure the 44.45mm is a backspace spec and not something else?
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Old 12-01-2017, 01:04 PM
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Quote:
Originally Posted by realshelby View Post
Rubicon wheels are 17", not 18".
You are correct, my mistake. I fat-fingered that one and for some reason I cant edit my original post. that not allowed around here??


Quote:
Are you sure the 44.45mm is a backspace spec and not something else?
That is definitely the offset value, not backspace. its stamped on the rim and here is an online reference.

ALY9118.LC29HH Jeep Wrangler Wheel Grey Machined #1XA50TRMAA
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Old 12-01-2017, 01:42 PM   #5
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it is easy to measure. take your spare and lay a flat edge on the rim (bead to bead) and measure from the hub and it will be 6.25"
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https://www.wranglerforum.com/f314/y...i-2192385.html
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Old 12-01-2017, 01:57 PM   #6
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I suspect offset ( no idea what that actually refers to ) and backspace are two different things. I have seen here where a ruler and straightedge are used to show backspace and it is right at 6 1/4".
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Old 12-01-2017, 02:05 PM
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Offset the the distance from the centerline of the rim to the mating surface of the rim/hub

Backspacing is suppose to be the distance from that same mating surface to the rear of the rim.

Ideally those numbers should add up, but if real world measurments are 6.25"........ my question now is WTFs up with the 3/4" discrepancy????
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Old 12-01-2017, 02:10 PM   #8
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bead thickness perhaps.
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https://www.wranglerforum.com/f314/y...i-2192385.html
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Old 12-02-2017, 12:14 AM   #9
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I think you have to add 0.5" to each side of the 7.5" width to your calculations to get the right results. (For the lips.)
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Old 12-02-2017, 12:21 AM   #10
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Here is a calculator. It gives a backspace of 6.00" when you use the default lip width of 0.5".

Wheel Offset/Backspace Calculator - Calculate/Compare Wheel Offset and Backspace

It will return 6.25" backspace when you use a lip width of 0.75".
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Old 12-13-2017, 10:25 AM   #11
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Listed rim width and actual width are 2 different numbers, I believe that's where the difference comes in
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Old 12-20-2017, 05:20 AM   #12
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Depends who is measuring too, some use the bead seat, others the outer edge of the rim...
Same thing with tire sizes and so many variances with them among manufacturers...

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