🧐 Are 37x12.5’s on Stock Rims Safe?

DOTCOM

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I’m seeing mixed messages when researching to see if 37x12.5’s are safe to put on our stock rims.

Any experts here able to clear the air?

Thanks in advance!

Chris
 

YukonCornelius

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Not really safe (most places won't install either.) If you look at the specs for 37" by 12.5" tires from the usual players (BFGoodrich, Toyo, Cooper, Nitto, Goodyear, etc) they all have minimum wheel width as 8.5. Heck, in my experience, I wouldn't personally go narrower than 9" for 37's.

The stock rims could go with 35x11.5's - but I think Nitto is the only one really making a decent tire at that size.

edit: @Riddler pointed out Toyo AT III’s as well (y)
 
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mattcarvette

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Has anyone found a wheel that is a close aesthetic match to the stock rims but is at least 8.5" wide? I like the look, but want 37s!
 

BenLandry

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Before and after fuel Rebels. These are 37x13.5 on 20x10 but I’m fairly certain they are made smaller diameter and width. Pretty close I think. Dirty Life makes one pretty close also
 

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hardhat

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It is fine to run on stock 7.5 rim. I ran 35x12.5 and 37x12.5 km2s wheeling with no problem. Had 37x12.5 ko2 on stock 2013 rubicon rim for over 60k miles now. Run 28 psi per aev lift recommendations and have been very happy. The lower pressure helps tire run flatter on the narrower rims. Running spidertrax 1.5 spacers. Check torque on spacers every tire rotation. They are on with red locktite and have never budged. I like my stock rims and lots of people run the wider tires on stock rims. It is only a little out of spec. I felt comfortable doing it but I watch my stuff carefully. 2013 jjku rubicon with 96k miles. 392 ordered and hopefully will get here eventually
 

YukonCornelius

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It is fine to run on stock 7.5 rim
No reputable installer should be doing that. They will go with tire manufacturer's recommended/required wheel specs, and in the case of pretty much all branded 37x12.5's is about an inch too narrow at 7.5 to be safe. Can you do it" Sure. But when you pop a bead rounding a corner a little aggressively don't say you weren't warned.

And unless you’re always running locked beads even for daily driving, if the rim is too narrow for the tire, it causes the tire have more lateral movement than it was designed for. Not safe. If the rim is too narrow for the tire, it causes it to "bow" or bulge outward, weakening the sidewall. Also not safe.
 
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hardhat

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No reputable installer should be doing that. They will go with tire manufacturer's recommended/required wheel specs, and in the case of pretty much all branded 37x12.5's is about an inch too narrow at 7.5 to be safe. Can you do it" Sure. But when you pop a bead rounding a corner a little aggressively don't say you weren't warned.

If the rim is too narrow for the tire, it causes the tire have more lateral movement than it was designed for. Not safe. If the rim is too narrow for the tire, it causes it to "bow" or bulge outward, weakening the sidewall.
Can’t argue with specs. Safest thing is to get new rims that have appropriate width and backspacing.

But lots of people have run wider tires on stock rims with spacers. I couldn’t find a failure story in my brief search. Have heard of spacers coming off which would be terrible but red loctite and keeping your eyes open for problems reduces this risk. I think the spacers have more risk than the wider tires on narrow rim. I’ve run 60k miles on my 37x12.5 ko2 on stock 17 x whatever rubicon rims. They still have tread left and 28 psi has helped with uneven tire wear but they have worn more in center. Still serviceable. Just do some research and make an informed decision. I would’ve bought new rims but I liked those stock rubicon wheels.
 

Riddler

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Not really safe (most places won't install either.) If you look at the specs for 37" by 12.5" tires from the usual players (BFGoodrich, Toyo, Cooper, Nitto, Goodyear, etc) they all have minimum wheel width as 8.5. Heck, in my experience, I wouldn't personally go narrower than 9" for 37's.

The stock rims could go with 35x11.5's - but I think Nitto is the only one really making a decent tire at that size.
Doesn’t Toyo make the ATIII in 35x11.5x17 that is specced for 7.5” wheels?
 

mmsmab1

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Before and after fuel Rebels. These are 37x13.5 on 20x10 but I’m fairly certain they are made smaller diameter and width. Pretty close I think. Dirty Life makes one pretty close also
How do you like how it drives and handles with the 37's?
 

BenLandry

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How do you like how it drives and handles with the 37's?
It drives 100 times better than my supercharged JK on 37s. I’m so used to passing cars at full throttle with my JK that when I pass now I routinely see 97-98 mph…not on purpose. The point is that at that speed it’s still riding really smooth. I did upgrade the stabilizer to a Fox. I don’t recommend weaving in and out of traffic too hard but I do sometimes just because I can. There was a little loss of power I feel on the higher end but not much launching, the pedal commander helps out with that….at least in my mind it does, it absolutely jumps off the line, especially in launch mode
 

Ward

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Has anyone found a wheel that is a close aesthetic match to the stock rims but is at least 8.5" wide? I like the look, but want 37s!
Stock 392 wheels are safe up to 40's. They are also headlock capable wheels. Here is my 392 on 37's with AEV 17x8.5 and I love them, these spent 3 years on my JK until we bought the 392.
 

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YukonCornelius

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You’re running 8.5’s. Stock is 7.5
7.5’s are NOT safe for 40’s
 

koszuta

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If I have the factory reinforced tire carrier, what else do I need to hold a 37 tire on back?
 

Lulu

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We're putting Anthem 17x9s on ours and looking to get 37" GENERALS. There's a concern raised on whether the axles need to be upgraded to handle it for off-roading. Any thoughts?
 

BenLandry

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If I have the factory reinforced tire carrier, what else do I need to hold a 37 tire on back?
A spare relocation kit…mopar makes one, I have the Teraflex HD carrier, it comes with a third brake light relocation bracket. Otherwise your tire won’t clear the bumper
 

hardhat

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We're putting Anthem 17x9s on ours and looking to get 37" GENERALS. There's a concern raised on whether the axles need to be upgraded to handle it for off-roading. Any thoughts?
Depends on how you hard you drive it. I had my 2013 front axle sleeved and gussetted for running 37's. Never had a problem with stock axle shafts or u joints. Have heard reports of people bending axles with 37's but have never seen it in person. Some say that on road maneuvers can stress axles just as much (hitting potholes at speed going around a curve).

Just my thought that the stock axles would be OK on 37's since they say the rubicons can run 35s without mods....37 is not that much bigger.....I plan on running 37s in the future and plan to do it on stock axles.
 
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