JL Offset & Backspacing Finally Answered!

[JasonInDLH]

This thread really does not give anyone any good information without telling us how much bumpstop front and rear. Rubbing or not rubbing is usually because of the amount of bumpstop.

Good point! I was thinking the OP was meaning steering lock to lock rubbing on a flat surface. I didn’t even consider rubbing while flexing.

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[Cavs42]

35s on -15 backspacing with no lift WILL rub on full flex. Otherwise it is absolute money.

 

[DLW]

Might have this all wrong, I thought the best offset/backspace would be one that gives proper/best scrub radius? Otherwise it is a compromise for getting clearance. This is why wider axles are available with larger tires (amongst other things like strength) to overcome some of the clearance issues and maintain good scrub radius. There is a couple really good threads about scrub radius by smarter folks than me I found very informative.

 

[blnewt]

Might have this all wrong, I thought the best offset/backspace would be one that gives proper/best scrub radius? Otherwise it is a compromise for getting clearance. This is why wider axles are available with larger tires (amongst other things like strength) to overcome some of the clearance issues and maintain good scrub radius. There is a couple really good threads about scrub radius by smarter folks than me I found very informative.

Good post!
I think scrub radius takes a back seat around here, many just get the wheel/tire they like and if it fits it's all good. IMO it's best to get the offset closest to stock that allows full suspension flex. Of course those w/ 4+ inches of lift w/ huge tires are going to have to throw scrub radius out the window and just deal w/ having steering geometry out of whack unless you plan on plenty of bump stop.

Luckily w/ the trails I want to run and keeping a lower center of gravity build I can keep the scrub pretty close (running an 8.5 +10 offset). I have 315/70s ready to install, been saying that for over a year, but w/ the gas prices I haven't driven it enough to wear out my current 295/70 Patagonias.
I did add an inch of bump so hopefully that's all I will need to go w/ the bigger tires, time will tell

 

[DLW]

Good post!
I think scrub radius takes a back seat around here, many just get the wheel/tire they like and if it fits it's all good. IMO it's best to get the offset closest to stock that allows full suspension flex. Of course those w/ 4+ inches of lift w/ huge tires are going to have to throw scrub radius out the window and just deal w/ having steering geometry out of whack unless you plan on plenty of bump stop.

Luckily w/ the trails I want to run and keeping a lower center of gravity build I can keep the scrub pretty close (running an 8.5 +10 offset). I have 315/70s ready to install, been saying that for over a year, but w/ the gas prices I haven't driven it enough to wear out my current 295/70 Patagonias.
I did add an inch of bump so hopefully that's all I will need to go w/ the bigger tires, time will tell

Very good points. I also made the same, for lack of a better word, mistake choosing 3.5" BS wheels on stock Rubicon axles when I went with 38's. I did not understand scrub radius at the time or I would have chose a different route I think. I'll be going 1 tons at some point where I will need new wheels anyway, and will have to choose someone that offers wider axles, so that put's UD60's out.

Liking that Avatar in your sig

 

[El Zilcho]

• JL Model: Sport with Rubicon axles
• Wheel: AEV Pintler JK version
• Offset: +10
• Backspacing: 5.2"
• Tire Make: BFG KO2
• Tire Size: 315/70 17)
• Lift: 0 (rubicon springs) or 2"
• Rubbing: Rubs fender liners with no lift, fine with 2" AEV spacer lift(1.5 or 2" bumpstop)

 

[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.

 

[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.

 

[DLW]

I'm just the opposite, I kinda hate dealing with offset (dam metric system), backspace is what I grew up using and just makes since to me, it tells me everything I need to know if I have the wheel width. Last time I ordered custom wheels from Billet Specialties, they asked for a lot of measurements, but offset was not one of them, backspace was. I know everyone seems to use offset nowadays, some wheel manufactures provide both even. You can figure out offset and backspace with either measurement though.

 

[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 subtracting 5mm of offset for every 2" increase in tire height will bring things back to stock by moving the tire/wheel out a bit.

 

[Obi.Wan.Shawnobi]

• JL Model: rubicon
• Wheel: AEV JL Pintler
• Offset: 5.77 +25
• Tire Make: cooper stt pro
• Tire Size: 37x12.5r17
• Lift: mopar approx 2.75
• Rubbing: eleminated rubbing at rear liners with heat reshaping and front LCA's with steering stops out 1/4"
• Pictures:
• 
  
  
  

Fellow Venturan here!

 

[Deleted member 85946]

I wish I had found this thread when I was shopping for wheels and tires!

• JL Model: Rubicon
• Wheel: Ballistic Rage
• Offset: -19mm
• Backspacing: 4.75
• Tire Make: BFGoodrich Mud Terrain KM3
• Tire Size: 325/60R20
• Lift: AEV DualSport 2.5”
• Rubbing: None
• Pictures:
• 
  
  
  
  
  
  
  
  
  
  
  
  
  
  

I was planning on running the same sized tire on a set of kmc km722 (20x9 w/0 offset) wheels.

Have you ever compared your tire side-by-side to a 35x12.50? If so, how much larger was it?

thanks in advanced!

 

[Muskoka Minute]

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.

So if I have a 286/70R17 (33" tire) with a 17x7.5" rim with 37 Offset.
And I go with a 35/12.5R17 (35" tire) with a 17x9" I would have to go with a 42 Offset to keep my scrub radius?

Is this correct ?

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