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Backspacing for JK/JKU with 315/70R17 or 35/12.5 tires?

5293 Views 9 Replies 4 Participants Last post by  White Elemant
Hi

I've been wrestling with the following problem for months: what is the biggest backspacing I can go with on my lifted 2016 JKU Wrangler with 17x9 wheels if I get 35 inch tires and do not want rubbing issues ? To be more specific the tires will most likely be BFG T/A ko2's, in size 315/70R17 (simply because of availability issues here in the periphery of Europe. So:

I'm looking for first hand info / definitive answer for the question of "What is the maximum backspacing of 17x9 wheels on Wrangler JKU with with 2" lift and 315/70R17 tires without rubbing? Answers for 35/12.5R17 will also do, as the tire size is pretty much the same.

Based on plowing through the internet I'm very confident 4.5" will work, pretty confident 4.75" backspace will work. 5" backspacing, not convinced, yet... only .25" / 6mm difference to 4.75", but... So 4.5" backspace can be settled as a known known (as per Donald Rumsfeld). My most intense interest is towards the 5" end of the spectrum...

Sorry in advance, but I'm not interested in
  • "I'm pretty sure..."
  • "I heard..."
  • "For 285/75R17...", goes for any other smaller diameter or narrower tire / different wheel size from what is specified in the actual question.
  • "Why do/don't you... / You should..."
  • Any other commentary not answering the question (other than pointing out a mistake in the question, of course).
Reason for being a nag about this is that this kind of threads get polluted very quickly with chaff and chatter. Plus if I wanted to guess, I'd just guess on my own.

I'm asking because
  • Local regulations are a pain in the ass when it comes to increase in track, and tires sticking out.
  • I want 315/70R17 tires. Period.
  • I want 17x9 wheels. Also period.
  • I want minimal extra strain on ball joints, knuckles etc: bigger backspace=better.
  • Sourcing exact information has been difficult.
  • I know there are a lot of helpful folks here.
I'm aware that
  • Being such a nag prolly pisses off some.
  • Most of you did not read this far because of the former / ADT / ADHD / other reasons.
  • I may get varying results depending on tire brand / model.

Thanks!
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I bet you're a blast at parties 馃槢

Not pointing out a mistake in your question, but you're not providing enough info for the cut and dry answer you seem to want. Rubbing issues how? Normal on-road driving, or fully stuffed and disconnected off-road? What lift kit? Does your lift manufacturer list a minimum backspace to avoid rubbing their end links? Are you factory arms but lifted? Did you add adjustable arms to move your axles? If so how far did you move them? etc, etc, but I think you get the idea.

In general (because you only gave us enough info for a general answer):

On road:
5.2" or less. 5.2" is what AEV uses as it's backspace on most of their wheels with a 35/12.5" tire in mind. They are considered by most to be experts, but their wheels are 8.5", not 9". I personally prefer 4.5" on mine when running a 35/12.5", but with your restrictions that' doesn't sound like what's best for you.

Off road:
All depends on your suspension set-up, can't give an answer without knowing all the details.

In your situation I would look at an AEV wheel or one that is comparable in spec. And if you get slight rubbing in certain situations, so be it. It won't be intolerable. AEV verbiage below:

4495458


4495459
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Typically anything with 5.2" of backspacing or less will work with a 12.5" wide tire.
AEV wheels are incredibly popular and most tend to mount a 35x12.5 tire (or equivalent) on them and they work fine. We ran a set of AEV wheels with 37x12.5 tires and had a very small amount of rubbing when turning all the way. WIth a 35" tire it would not have rubbed.
Another brand of wheels that use 5.2" of backspacing as their standard spec is Quadratec. They offer a number of wheels with 5.2" of backspacing that are also hub centric. And they are reasonably priced.
You don't see much that are 5" of backspacing, mostly from 5.2" it jumps to 4.75" followed by 4.5". Any of those three backspacings should work fine. I would avoid going to 4" or less if you don't have to.
As mentioned, what suspension you have can play a part. If you have shocks that allow for a lot of droop that may cause rubbing when one side is full stuff and the other side is full droop. MetalCloak RockSport shocks would be an example of shocks with more droop than most. Even their 2.5" lift uses shocks that are longer than most 2.5" lift shocks fully extended.
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Thanks for both, much appreciated!

Yea, 5" backspace is hard to come by, but I've been drooling at these: G-FX TR16 17x9 0 Black | T16 790-5127-00 MB | Custom Offsets
These have the 5" backspace (0mm ET) and the 8-hole design I adore.

Thing with rubbing is, it's also one of the absolute no-no's at local vehicle inspection, so if the inspector notices any, you gotta change the setup and go back with something less agressive.

I currently have a 2.5" spacer lift done by previous owner, and stock shocks that limit travel. I will upgrade the shocks this summer, and prolly do control arms, sway discos and springs within about a year.

There's very little agressive offroading opportunities here, so that's not really what I aim for. White Elemant is my daily drive, so I gotta make some compromises, and I prolly wont be punishing it too much. It's just too expensive of a car for me to break...

P.S. yea I'm no fun at parties till I get drunk 馃お
It also depends on the side lugs of the tire you choose. 4.75鈥 BS on 17x9鈥 wheels rubs bad with 37x12.5x17 Pitbulls.


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As my weapon of choice will be (90% sure) BFG T/A ko2, I'm not that worried about the side lugs. It seems tread width and side lugs of this tire are rather conservative. + the size I aim for is an inch less in radius.
Ok, happened so far:
G-FX TR16 17x9 by V枚xx Wheels from Custom Offsets arrived last friday. Only took about two weeks to my door (mind you, I'm in Finland).

Delivery surprised me, so tires will arrive on 11th, and they ar T/A ko2's in 315/70R17

I'll let ya know how they fit...
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Ok, tires (finally) being installed as i write.

They look A LOT bigger than I thought 馃槀
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Concise report: perfect fit.

315/70 R17 BFG T/A KO2
17x9 ET 0 , backspace 5" wheel.

Previous owner had trimmed the airdam top outer corners just a bit, those might have rubbed otherwise.

Tread sticks 1/2" outside fender.

I'll report more in a couple of days.
I'm so freakin happy with this setup!!!
2
Flex report.

With 2.5" lift, stock shocks (yes I know, criminal), no disconnects:

Rear needs about an inch taller bump stops, just barely rubbing on fender.

Front not even close.
4513655

4513656
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