Wheel backspace ?

[BobK]

Great video. That is the aggressive look I want!!!!!

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[Jeepsk8]

315-70/17's on ProComp steelies, 17X9 with 4.25" backspace, no idea what that offset equates to. No lift either.

Keep in mind, offset is distance from centerline of the wheel. Any negative offset will push the centerline away from the vehicle. On a 9" wheel, 0 offset will give you 4.5" backspace. They are directly related.

 

[Chocolate Thunder]

On a 9" wheel, 0 offset will give you 4.5" backspace. They are directly related.

I’ve looked at a number of 9” wide wheels but they have -12mm offset that equates to 4.53” backspace. 0 offset on 9” is 5” backspace.

 

[Jeepsk8]

I’ve looked at a number of 9” wide wheels but they have -12mm offset that equates to 4.53” backspace. 0 offset on 9” is 5” backspace.

And here is where the industry contradicts itself. If you Google offset/backspace they define 0 offset as wheel hub mounting surface in line with the centerline of the wheel. But, for some reason, the calculators and charts say something different. Most wheel companies will give both measurement of you ask for them, backspace being the most applicable to our needs.

 

[Chocolate Thunder]

And here is where the industry contradicts itself. If you Google offset/backspace they define 0 offset as wheel hub mounting surface in line with the centerline of the wheel. But, for some reason, the calculators and charts say something different. Most wheel companies will give both measurement of you ask for them, backspace being the most applicable to our needs.

You are correct.

 

[TroyBoy]

For those that are offset/backspace challenged this tool does all the work and presents the answer in a visual format that is easier for most people to understand. Just plug in the numbers on the current tires/wheels and the new ones.

https://tiresize.com/wheel-offset-calculator/

That is a nice calculator

 

[Chocolate Thunder]

That is a nice calculator

There’s a number of really useful ones on that site. Offset/backspace, tire size and comparison, speedometer correction, gear ratio. Most have visuals which help most people understand the concepts better.

 

[Pig-Pen]

I’ve looked at a number of 9” wide wheels but they have -12mm offset that equates to 4.53” backspace. 0 offset on 9” is 5” backspace.

this is correct.

you convert the offset in mm to offset in inches. so -12mm/25.4= -.47"

then you add the -.47" to 1/2 of the wheel's "true width" (outer edge to outer edge which is always 1" wider than the stated width).

so on a 9" wheel, you add -.47"+5"= 4.53" aka -12mm offset on a 9" wheel is 4.53" backspacing




if we have an 8.5" wheel with -12mm offset...

-12/25.4= -.47" (same offset in inches)

then you add the -.47" to the 1/2 of the wheel's "true width" which is 4.75" (8.5+1 then divided by 2).

so on an 8.5" wheel, you add -.47"+4.75"= 4.28" aka -12mm offset on an 8.5" wheel is 4.28" backspacing (sticks out more)

**less backspacing means more "front spacing" which means more deep dish ala sticking out more.


to convert from backspacing to offset, just do the opposite of above
4.28"-4.75"= -47" offset in inches. then convert that to mm -47*25.4= -11.938mm (slightly under due to rounding)


**however "wide" your wheels are, they are always 1" wider in their true width. this is because the industry counts the width of the wheel between the tire bead flanges. the flanges are 99% of the time, .5" wide on each side, ie an extra 1" overall. so when measuring backspacing and offset that of course comes in to play as it affects the numbers. your number is will be way off if you do the calculations using the standard width of the wheel. of course, online calculators do this for you so you just put in the stated width of the wheel. next time you have a rim with the tire off measure it from outer edge to outer edge and you will see what i mean. we had a customer order 9" wheels once. he received them and i guess measured them for the heck of it. he started freaking out called me all upset that he wanted 9" wheels and we sent him 10"!!! he was measuring the wheel from the outer edge to outer edge, ie 10". he checked while we were on the phone and said "oh. it's 9"

this page right here gives a perfect visual aid
https://www.more-japan.com/blogs/2011/08/24/how-to-measure-wheel-width/

this page gives a good visual aid for measuring a wheel's backspacing and converting offset as i stated above
https://www.more-japan.com/blogs/2011/08/23/how-to-find-out-the-offset/

And here is where the industry contradicts itself. If you Google offset/backspace they define 0 offset as wheel hub mounting surface in line with the centerline of the wheel. But, for some reason, the calculators and charts say something different. Most wheel companies will give both measurement of you ask for them, backspace being the most applicable to our needs.

no, not really. no offense. you either found a page with the wrong info or you possibly interpreted it wrong. ive been in the wheel business since the TJ days. spent quite a bit of time in the wheel hall at sema. everyone uses the same calculations. its basic math. its not like the tire industry where they measure the width of a tire from different locations on the tire. its standard for wheels.

measuring backspacing is super easy. to measure the backspacing of a wheel, you lay it face down on the ground, lay a straight edge over the back of the wheel (preferably sans tire) then measure straight down to the mounting pad surface. that's your backspacing. that is always correct, when you measure it yourself.

some times wheels arent exactly how wide they are supposed to be, for instance a 9" wide wheel which should measure 10" actually measures 9.75" or 9.85" but this is not typically on cast wheels which are made using a mold. moreso on custom made forged wheels. but then when they assemble the wheel, they take this into account and adjust accordingly.


in my experience and opinion, backspacing is far easier and more reliable to deal with than offset. you do need to know how the wheel is though.



**only time ive seen this, but we pulled an oem wheel off a 70s/80s model ferarri. the wheel was 8.75" wide. that was an oddball for sure.

 

[PavementWarrior]

Step one start looking at offset and use the visual tool to see results

 

[Jeepsk8]

no, not really. no offense. you either found a page with the wrong info or you possibly interpreted it wrong. ive been in the wheel business since the TJ days. spent quite a bit of time in the wheel hall at sema. everyone uses the same calculations. its basic math. its not like the tire industry where they measure the width of a tire from different locations on the tire. its standard for wheels.

Definitely not offended. However, I do have a pretty good grasp on the English language and I'm pretty good at interpretation. So when a site like... oh I don't know... Discount Tires Direct, has a diagram and clearly states:

ZERO OFFSET

"The mounting surface is centered within the rim, aligned with the wheel’s centerline."

Copied right from their site, not sure how else I'm supposed to read that. The unaccounted for variable is the width measurement, and silly me, took 9" wheel width to mean 9". My simple brain did a little grade school math and divided 9 by 2 and got 4.5. That is how I got 0 offset to equal 4.5" backspace on a 9" wheel. Now that I know 9" isn't REALLY 9", and simply plugging in some metric system stuff, because hey, why not, a 9" wheel (that isn't really 9", remember) with a 4.5" (not metric) backspace has a -12mm (there it is) offset.

This is all in fun, I am a smart ass, that's how I roll. But seriously, I really didn't understand how -12mm offset was figured, now I know and I do thank you for pointing that out.

 

[Pig-Pen]

Definitely not offended. However, I do have a pretty good grasp on the English language and I'm pretty good at interpretation. So when a site like... oh I don't know... Discount Tires Direct, has a diagram and clearly states:

ZERO OFFSET

"The mounting surface is centered within the rim, aligned with the wheel’s centerline."

Copied right from their site, not sure how else I'm supposed to read that. The unaccounted for variable is the width measurement, and silly me, took 9" wheel width to mean 9". My simple brain did a little grade school math and divided 9 by 2 and got 4.5. That is how I got 0 offset to equal 4.5" backspace on a 9" wheel. Now that I know 9" isn't REALLY 9", and simply plugging in some metric system stuff, because hey, why not, a 9" wheel (that isn't really 9", remember) with a 4.5" (not metric) backspace has a -12mm (there it is) offset.

This is all in fun, I am a smart ass, that's how I roll. But seriously, I really didn't understand how -12mm offset was figured, now I know and I do thank you for pointing that out.

there is nothing wrong with the graphic you posted. you said you found other stuff that contradicts that.

 

[Yellow109r]

backspacing

http://www.galantvr4.org/docs/backspacing.htm

 

[PapaJoe]

Sahara and Rubicon offset is the same, just diameter is different. My new rims are 17"x9 with -12mm offset. Here is what the 34" ridge grapplers look like on mine. Check out this thread, lots of pictures from a few different people that have gone this route. There are a few other threads as well and a few with 37", they seem to look good as well.

https://www.jlwranglerforums.com/forum/threads/285-75r17-on-sahara.3609/

Also, a really good site to check out is https://www.rimsntires.com/specspro.jsp they have a great app that graphically shows the differences.

Jeez, those look HUGE for 34s! Is there some flexing going on in the rear tire in that side shot that makes them look like they fill up the wheel well more, especially with the lift? The front looks more like I'd expect. I have a JLUS with 1.5" leveler on the front and am debating between 285/70/17 and 285/75/17. I like the fuller wheel well look, but don't want to rub. I don't plan on rock-crawling, but would like to take it on trails.

 

[Jeep Newb]

I really don’t get this whole wheel thing. Can someone tell me if these will work on a jlu Rubicon? I don’t want the tires to stick out much? Putting toyo at2 35” tires on the 18” rims.

 

[Chocolate Thunder]

I really don’t get this whole wheel thing. Can someone tell me if these will work on a jlu Rubicon? I don’t want the tires to stick out much? Putting toyo at2 35” tires on the 18” rims.

That wheel will protrude 2.34” more than stock rubicon wheels.

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