Wheel Backspacing

OFC Ranger

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I'm looking at going from a factory wheel that has 6.7" backspacing to a wheel that has 4.5" backspacing.

Now lets throw a wrench into this further. I run 2" spacers giving me an offset of +5 (55+ minus 50 negative) and the new wheels with no spacer is -12 offset. (I wont be running the spacers)

I understand 100% how offset works, but even reading around the web, backspacing has me still a bit confused. Anyone shine some light?

Does backspacing give the wheel more of a deep lip?
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Frenchy

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So if you watch this video it should help you out as explains oddest and backspacing. Also the pros and cons of it. I watch this particular offroaded since he has a lot of good general information.

 
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OFC Ranger

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So if you watch this video it should help you out as explains oddest and backspacing. Also the pros and cons of it. I watch this particular offroaded since he has a lot of good general information.
I did not hear him address backspacing - unless I missed it. I get that backspacing is just another measurement of offset. Or is it the same thing as offset?

I can find charts showing wheel width and backspacing.

So 4.50" on a 9" wide wheel = -12mm offset

So I can just say, "My wheel is -12mm offset" or "My wheel has 4.50" backspacing" and they both mean the same thing?

EDU_wheel-offset-backspacing-conversion-chart.jpg
 

Frenchy

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I did not hear him address backspacing - unless I missed it. I get that backspacing is just another measurement of offset. Or is it the same thing as offset?

I can find charts showing wheel width and backspacing.

So 4.50" on a 9" wide wheel = -12mm offset

So can either just saying, "My wheel is -12mm offset" or "My wheel has 4.50" backspacing" and they both mean the same thing?

EDU_wheel-offset-backspacing-conversion-chart.jpg
Back spacing is just the measurement from the mounting surface to the back of the wheel. It is something you dont have to worry about much if you already know the offset and width since you can make the necessary calculations with that.
 


HenryMac

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Back in the day the only information available was backspacing and wheel width.

I never understood why "offset" came into the picture? It was always there... nobody talked about it, it just further complicates things IMO.

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Back in the day the only information available was backspacing and wheel width.

I never understood why "offset" came into the picture? It was always there... nobody talked about it, it just further complicates things IMO.

1979 - 1977 Nova.jpg
+1 on that John !
 

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They are 2 completely different measurements. You can calculate one from the other. For offset to backspace you need the rim width divided by 2 +or- the offset + the width of the wheel lip

Example an 8" wide wheel with +25.4mm offset(+1"offset) wheel lip of 12.7mm(.5" lip width)
8/2=4 4+1=5 5+.5=5.5" backspacing

Change to a 8.5" wide wheel with the same +25.4mm offset and it has a 5.75" backspacing so just stating your offset without the rim width and a little math tells you nothing.

Backspacing is a more useful measurement for things like spindle to wheel clearance. Say 5.5" backspaced wheel clears but 5.75" does not. A manufacture can just say it requires a maximum of 5.5" of backspace to clear. The wheel width does not matter in this instance because backspace does not change if wheel width changes.
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