Back spacing and offset

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Michaelg1991

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Guys looking at pro comp 7069 wheels for my Tj.
I have ordered brand new 245/75r16 tyres. The new wheels are 16x8 with a negative 12.7mm offset and 4 back spacing. Will all these measurements work correctly. The bolt pattern is correct at 5x4.5
Thanks
 
Ignore the offset and focus on backspacing.

Offset is the distance from the center of the wheel to the part that actually mounts to the drum/rotor.

Backspacing is the distance from the part that actually mounts to the drum/rotor to the back of the rim.

The original 16" Jeep Moab wheels had 5" back spacing and 245/75r16 tyres from the factory. With 1" less backspacing you should never rub against any frame or suspension parts. The 1" less back spacing will push the wheel out 1" but it probably would take some crazy off road attempts to rub on the fenders.


For some reason I've seen at least a few wheels advertised where doing the math between backspacing and offset don't match. Even the 16x8 with a negative 12.7mm offset and 4 back spacing just mentioned doesn't work out.

With the center of an 8" wide rim being 4" and the backspacing being 4" it sure looks like the offset would be 0.0mm. Maybe someone can set us straight about that.

​

 
JeepCJTJ is spot on. Even a 4 1/2" backspace should work until you start putting 13 1/2" tires on. At that point you would want a wider rim anyways.👍
 
X2 to all the advice above, especially on forgetting you ever heard the term offset, we only care about backspacing on Jeep and truck wheels. Offset is a measurement that is used for car wheels. Focus solely on backspacing for your Jeep wheels and life will be easy. :)
 
Thanks guys that’s a massive help. Is any one uk based?
I tell you for what, ordering items from quadratech is a nightmare because of the shipping costs and import taxes. By the time you have got the items in the uk you pay the same almost in shipping and taxes as the actually bill from the items
 
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JEEPCJTJ said:
For some reason I've seen at least a few wheels advertised where doing the math between backspacing and offset don't match. Even the 16x8 with a negative 12.7mm offset and 4 back spacing just mentioned doesn't work out.

With the center of an 8" wide rim being 4" and the backspacing being 4" it sure looks like the offset would be 0.0mm. Maybe someone can set us straight about that.
Click to expand...
I came across the same issue when I was answering a similar thread the other day. Turns out offset is measured from 1/2" off center. Weird, don't know why.

offset.jpg
 
JEEPCJTJ said:
Ignore the offset and focus on backspacing.

Offset is the distance from the center of the wheel to the part that actually mounts to the drum/rotor.

Backspacing is the distance from the part that actually mounts to the drum/rotor to the back of the rim.

The original 16" Jeep Moab wheels had 5" back spacing and 245/75r16 tyres from the factory. With 1" less backspacing you should never rub against any frame or suspension parts. The 1" less back spacing will push the wheel out 1" but it probably would take some crazy off road attempts to rub on the fenders.


For some reason I've seen at least a few wheels advertised where doing the math between backspacing and offset don't match. Even the 16x8 with a negative 12.7mm offset and 4 back spacing just mentioned doesn't work out.

With the center of an 8" wide rim being 4" and the backspacing being 4" it sure looks like the offset would be 0.0mm. Maybe someone can set us straight about that.

​

Click to expand...
It's really on a technicality of how they measure the BS/offset/width

What happens is the width is measured from the inside of lip (bead)....
to other side inside lip (bead)..

So in your example 12.7mm is exactly half of an inch.
They use the inner bead seat to the mounting face as their backspacing...

the offset....
Using the overall width of the wheel (not bead seat to bead seat) to get to the half way mark...
in your example would be an extra inch.(half inch per side) Now we're at 9 inches overall width and half of that is 4.5
The back spacing goes from the mounting face to the usable width...
Hence having an 8" wheel (usable width) but a -12.7mm offset measuring to the actual outside width overall thus adding the extra 1/2 inch into the measurement.

Hope that helps....
 
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Mall crawlers were around years, decades even, before the stupid Fast and Frivolous came around.
They had those poser vehicles back in the 50's, and probably since the 2nd Model T was sold.
 
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