Wheel Fitment, Back Spacing, Width and Offset - Calculations and Considerations

[Old Dogger]

This is a topic, that it seems like has been discussed and mis-understood on vehicle forums ongoing.
First off, one doesn't need to be concerned about offset. With a wheel the concerns are the size 17",18", or larger, or smaller. mounting bolt pattern, proper mounting hole to stud size, Rim width and back spacing. And let's not forget price..LOL Most by far will use a 17", or 18" wheel, with a Rim width of 8.5" to 9.0", with a Back Spacing of 5.2 to 4.5. Most any size tires that we choose to run, will work good with this combination.

Below is more info that may help, example how to measure Back Spacing.:

^^^ The reason that knowing a offset number, is not really needed, is Because it changes by Rim width. EXAMPLE: A 8.5" RIM WIDTH, WITH A BACK SPACING OF 4.5 SHOWS A OFFSET OF -6. BUT WITH A 9" RIM WIDE, AND THE SAME BACK SPACING OF 4.5 SHOWS A OFFSET OF -12.
SO PLEASE, DONT BE CONCERENED ABOUT OFFSET. CONCENTRATE ON RIM WIDTH AND BACK SPACING, PLUS WHAT HAS BEEN MENTIONED ABOVE. BUT FOR THOSE OF YOU THAT FEEL MORE COMFORTABLE WITH OFF-SET! THERE IS CHART ABOVE FOR THE CONVERSION.

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[Mocopo]

This is a topic, that it seems like has been discussed and mis-understood on vehicle forums ongoing.
First off, one doesn't need to be concerned about offset. With a wheel the concerns are the size 17",18", or larger, or smaller. mounting bolt pattern, proper mounting hole to stud size, Rim width and back spacing. And let's not forget price..LOL Most by far will use a 17", or 18" wheel, with a Rim width of 8.5" to 9.0", with a Back Spacing of 5.2 to 4.5. Most any size tires that we choose to run, will work good with this combination.

Below is more info that may help, example how to measure Back Spacing.:

^^^ The reason that knowing a offset number, is not really needed, is Because it changes by Rim width. EXAMPLE: A 8.5" RIM WIDTH, WITH A BACK SPACING OF 4.5 SHOWS A OFFSET OF -6. BUT WITH A 9" RIM WIDE, AND THE SAME BACK SPACING OF 4.5 SHOWS A OFFSET OF -12.
SO PLEASE, DONT BE CONCERENED ABOUT OFFSET. CONCENTRATE ON RIM WIDTH AND BACK SPACING, PLUS WHAT HAS BEEN MENTIONED ABOVE.

i was LITERALLY just having this convo with a buddy who bought his first jeep. He has a JLU sport with 33x12.5R22!!!! With like 2.5" backspacing.... ya it looks ridiculous, and he's trying to find the right wheel specs for a much more useable 33" tire. He kept talking about offset, you just explained it way better than they way I did to him...

 

[blnewt]

This is a topic, that it seems like has been discussed and mis-understood on vehicle forums ongoing.
First off, one doesn't need to be concerned about offset. With a wheel the concerns are the size 17",18", or larger, or smaller. mounting bolt pattern, proper mounting hole to stud size, Rim width and back spacing. And let's not forget price..LOL Most by far will use a 17", or 18" wheel, with a Rim width of 8.5" to 9.0", with a Back Spacing of 5.2 to 4.5. Most any size tires that we choose to run, will work good with this combination.

Below is more info that may help, example how to measure Back Spacing.:

^^^ The reason that knowing a offset number, is not really needed, is Because it changes by Rim width. EXAMPLE: A 8.5" RIM WIDTH, WITH A BACK SPACING OF 4.5 SHOWS A OFFSET OF -6. BUT WITH A 9" RIM WIDE, AND THE SAME BACK SPACING OF 4.5 SHOWS A OFFSET OF -12.
SO PLEASE, DONT BE CONCERENED ABOUT OFFSET. CONCENTRATE ON RIM WIDTH AND BACK SPACING, PLUS WHAT HAS BEEN MENTIONED ABOVE.

Good stuff, I've always went w/ offset, but backspacing is more common on the 4x4 sites, both will achieve the same basic fitment, just comes down to what you're used to.

 

[JasonInDLH]

This is a topic, that it seems like has been discussed and mis-understood on vehicle forums ongoing.
First off, one doesn't need to be concerned about offset. With a wheel the concerns are the size 17",18", or larger, or smaller. mounting bolt pattern, proper mounting hole to stud size, Rim width and back spacing. And let's not forget price..LOL Most by far will use a 17", or 18" wheel, with a Rim width of 8.5" to 9.0", with a Back Spacing of 5.2 to 4.5. Most any size tires that we choose to run, will work good with this combination.

Below is more info that may help, example how to measure Back Spacing.:

^^^ The reason that knowing a offset number, is not really needed, is Because it changes by Rim width. EXAMPLE: A 8.5" RIM WIDTH, WITH A BACK SPACING OF 4.5 SHOWS A OFFSET OF -6. BUT WITH A 9" RIM WIDE, AND THE SAME BACK SPACING OF 4.5 SHOWS A OFFSET OF -12.
SO PLEASE, DONT BE CONCERENED ABOUT OFFSET. CONCENTRATE ON RIM WIDTH AND BACK SPACING, PLUS WHAT HAS BEEN MENTIONED ABOVE.

I always want to know offset (and always start with offset) to give me a better idea how much wheel lip I’ll end up with. I know a -19 or -24mm offset will provide a good looking lip on a 10” wheel. I then double check the backspacing (which is always safe since I run aggressive offsets, but good to know just in case I go with a different wheel width/offset) to make sure I’m not rubbing on the inside.

At least this is how I have always ordered new wheels.

Sometimes there’s a method to my madness and sometimes I’m just mad.

 

[Kreepin1]

This is a topic, that it seems like has been discussed and mis-understood on vehicle forums ongoing.
First off, one doesn't need to be concerned about offset. With a wheel the concerns are the size 17",18", or larger, or smaller. mounting bolt pattern, proper mounting hole to stud size, Rim width and back spacing. And let's not forget price..LOL Most by far will use a 17", or 18" wheel, with a Rim width of 8.5" to 9.0", with a Back Spacing of 5.2 to 4.5. Most any size tires that we choose to run, will work good with this combination.

Below is more info that may help, example how to measure Back Spacing.:

^^^ The reason that knowing a offset number, is not really needed, is Because it changes by Rim width. EXAMPLE: A 8.5" RIM WIDTH, WITH A BACK SPACING OF 4.5 SHOWS A OFFSET OF -6. BUT WITH A 9" RIM WIDE, AND THE SAME BACK SPACING OF 4.5 SHOWS A OFFSET OF -12.
SO PLEASE, DONT BE CONCERENED ABOUT OFFSET. CONCENTRATE ON RIM WIDTH AND BACK SPACING, PLUS WHAT HAS BEEN MENTIONED ABOVE.

This is a valid approach, especially if you are considering a lift or other suspension component that has backspace requirements.

However, I prefer to think in terms of offset. We see a lot of posts on this board where someone asks for pictures and tire/wheel specifics to achieve a certain amount of "poke." The look is easy to recreate with the same tire size and wheel offset.

Personally, I like to fit the biggest tire possible with minimal lift. This often means a skinny tire that stuffs up into the wheel well when flexed. In the planning stage I flex the rig and measure how much clearance I've got with the existing tire/wheel combo. It's a lot easier to think in terms of offset change when figuring out how big a tire will fit.

Finally, as mentioned a few posts up scrub radius is often overlooked. Installing a taller tire reduces scrub radius and adding 5mm of offset for every 2" increase in tire height will bring things back to stock.

 

[J0E]

First off, one doesn't need to be concerned about offset.

SO PLEASE, DONT BE CONCERENED ABOUT OFFSET. CONCENTRATE ON RIM WIDTH AND BACK SPACING, PLUS WHAT HAS BEEN MENTIONED ABOVE. BUT FOR THOSE OF YOU THAT FEEL MORE COMFORTABLE WITH OFF-SET! THERE IS CHART ABOVE FOR THE CONVERSION.

Awesome post. But some places only give offset. For example, I have 37x13.5 KM3s on stock rims and I'm interested in this Velox wheel which is only $219 through Costco (and shipping for 5 wheels to Hawaii $168). They don't list BS, but have OFFSET:+10 and SUGGESTED TIRE SIZE:265/70R17. I don't understand suggesting a 265/70R17 for a 9" wide wheel.

 

[Old Dogger]

Awesome post. But some places only give offset. For example, I have 37x13.5 KM3s on stock rims and I'm interested in this Velox wheel which is only $219 through Costco (and shipping for 5 wheels to Hawaii $168). They don't list BS, but have OFFSET:+10 and SUGGESTED TIRE SIZE:265/70R17. I don't understand suggesting a 265/70R17 for a 9" wide wheel.

I agree, and would not run a 265 on a 9” wise Rim. I am currently running 275/70R17’s on 9” wide Rims. Discount tire installed them, and also said that they are a good fit. They are Falken Wildpeak A/T3W’s. C Rated….great tires..

 

[blnewt]

Awesome post. But some places only give offset. For example, I have 37x13.5 KM3s on stock rims and I'm interested in this Velox wheel which is only $219 through Costco (and shipping for 5 wheels to Hawaii $168). They don't list BS, but have OFFSET:+10 and SUGGESTED TIRE SIZE:265/70R17. I don't understand suggesting a 265/70R17 for a 9" wide wheel.

I guess if you're not planning to air down it will work ok, but not a great setup for a trail jeep for sure.

 

[LOBBS]

Thank you @Old Dogger !! This has been one of my pet peeves for years. Ever since offset became the more common way to spec out a wheel. It's meaningless without knowing the width, so you know the centerline that the offset comes from. But for Jeeps, backspacing is really what is important to clear suspensions since we have plenty of clearance to the outside for "poke".

 

[LOBBS]

Awesome post. But some places only give offset. For example, I have 37x13.5 KM3s on stock rims and I'm interested in this Velox wheel which is only $219 through Costco (and shipping for 5 wheels to Hawaii $168). They don't list BS, but have OFFSET:+10 and SUGGESTED TIRE SIZE:265/70R17. I don't understand suggesting a 265/70R17 for a 9" wide wheel.

You can calculate backspacing if you have offset and the wheel width.

 

[J0E]

I guess if you're not planning to air down it will work ok, but not a great setup for a trail jeep for sure.

I air down to 12. Why is this wheel unable to air down and not a great off-road setup?

 

[blnewt]

I air down to 12. Why is this wheel unable to air down and not a great off-road setup?

Not the wheel, just for that narrow 265 tire that was in that post.

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