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Tire Size?

392 firecrker

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Long time lurker, first time poster and first time buyer here. I just placed my order for a Firecracker Red 392 and I am soooo excited. So, my question is what would be the best tire size (35 or 37) if I want to stick with the 2" Mopar lift? Some of my confusion is from the reports written about the 392. First, I have read that the 392 has a 2" Mopar lift but it is only 1" taller than a standard Rubicon. Second, I understand that it is possible to fit 37" tires under the Rubicon without a lift but the tires do rub under flex. Do you think it will continue to rub with the extra 1" of room? Thoughts about the need for a thicker side-wall (e.g. D vs E) for extra handling ability due to the torque increase? (Leaning toward Cooper STT Pros) I noticed that the 392 concept had 37" tires and the GCM in the reveal had 35" tires (blue had 33"). Also, thoughts about 12.5 vs 13.5 width for the rims? It will be my daily driver but I will be taking my family camping with some frequency and get into some off-roading with my son. I understand that 13.5 will have more road noise but I have been told that the Cooper STT Pros can help mediate that some. Thanks for all the help and looking forward to becoming part of this neat community.
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BCMgunner

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12.5 wide tire is as wide as you want to go on the 7.5 inch rim.

The big unknown question is the backspacing on the 17x7.5 392 specific beadlock capable rims.

Stock 17x7.5 Rubi rims have 6.125” back spacing, and the 17x8 Mopar beadlock rims that have been available for years have a 4.4” backspacing.

To run 37” tires you’ll need 4.5” or less backspacing to confidently avoid rubbing on the suspension (lower control arms).

Anybody know the backspacing on the OEM 392 rims? Who can we ask to find out??
 

Whaler27

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Long time lurker, first time poster and first time buyer here. I just placed my order for a Firecracker Red 392 and I am soooo excited. So, my question is what would be the best tire size (35 or 37) if I want to stick with the 2" Mopar lift? Some of my confusion is from the reports written about the 392. First, I have read that the 392 has a 2" Mopar lift but it is only 1" taller than a standard Rubicon. Second, I understand that it is possible to fit 37" tires under the Rubicon without a lift but the tires do rub under flex. Do you think it will continue to rub with the extra 1" of room? Thoughts about the need for a thicker side-wall (e.g. D vs E) for extra handling ability due to the torque increase? (Leaning toward Cooper STT Pros) I noticed that the 392 concept had 37" tires and the GCM in the reveal had 35" tires (blue had 33"). Also, thoughts about 12.5 vs 13.5 width for the rims? It will be my daily driver but I will be taking my family camping with some frequency and get into some off-roading with my son. I understand that 13.5 will have more road noise but I have been told that the Cooper STT Pros can help mediate that some. Thanks for all the help and looking forward to becoming part of this neat community.
First, a 2” Mopar lift resulting in only a 1” height increase seems unlikely. The 392 will be heavier, but the Jeep should be built/sprung accordingly, so I doubt the effect of the lift will be fully cut in half.

There’s also significant risk of misinformation braided into the hype of any new model. The salesman who sold my brother his Jeep told him that Rubicon’s ”come stock with the factory lift” which, of course, they don’t. You need to really dig to get the details on the OEM suspension and lift, if any.

If no rub on full flex is the objective, the safest path is 35s. On the other hand, if you prefer the look, feel, and function of 37s, and you’re willing to pony up for a bigger lift if it’s necessary, go for the 37s and see what happens.

If the stock fit is too tight there will eventually be a good lift solution that allows full flex and good handling with 37s. If that’s what you really want, doing it up front is a lot cheaper than doing it incrementally over time.

If you’re thinking about 37” KO2s, they’re more like small 36s, so they’ll give you a little margin if you’re uncertain. They’ve been a good tire for me. The downside is poor performance in deep mud and a propensity to hydroplane on standing water. (The new studded 37” Grabbers I just mounted up as snow tires are taller with the Jeep sitting on them than my KO2s are unweighted.)

Finally, you definitely don’t want rims over 10”. A 9” rim/wheel will run the tires you’re considering, and there are a lot of 9” options with a -12 offset. (Also, remember the larger center bore required to accommodate the camera going through the spare — and the need for a tire carrier solution that will manage a 37” spare.)

I look forward to watching your build. You’ll be paving the way for the folks who follow with the 392. New models always mean new challenges. You’ll be the expert 18 months from now and the journey will be fun.
 
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Jamrock

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We really don't know yet.

I was surprised by some of the differences with the diesel Wrangler. The engine is much heavier than the ones used in the gas models, so FCA had to make adjustments. The diesel Rubicon has a different suspension from the gas. As a result 37 tires fit without a lift.

Many of the standard mods that work on the gas Wranglers won't fit properly on the diesel. For example, it took a while for the after market companies to bring diesel specific lift kits to market.

I would expect FCA to make adjustments with the 392 to compensate for the size/weight of the new engine. IMHO we just have to wait and see.



 
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Willy's Commando

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First, a 2” Mopar lift resulting in only a 1” height increase seems unlikely. The 392 will be heavier, but the Jeep should be built/sprung accordingly, so I doubt the effect of the lift will be fully cut in half.

There’s also significant risk of misinformation braided into the hype of any new model. The salesman who sold my brother his Jeep told him that Rubicon’s ”come stock with the factory lift” which, of course, they don’t. You need to really dig to get the details on the OEM suspension and lift, if any.

If no rub on full flex is the objective, the safest path is 35s. On the other hand, if you prefer the look, feel, and function of 37s, and you’re willing to pony up for a bigger lift if it’s necessary, go for the 37s and see what happens.

If the stock fit is too tight there will eventually be a good lift solution that allows full flex and good handling with 37s. If that’s what you really want, doing it up front is a lot cheaper than doing it incrementally over time.

If you’re thinking about 37” KO2s, they’re more like small 36s, so they’ll give you a little margin if you’re uncertain. They’ve been a good tire for me. The downside is poor performance in deep mud and a propensity to hydroplane on standing water. (The new studded 37” Grabbers I just mounted up as snow tires are taller with the Jeep sitting on them than my KO2s are unweighted.)

Finally, you definitely don’t want rims over 10”. A 9” rim/wheel will run the tires you’re considering, and there are a lot of 9” options with a -12 offset. (Also, remember the larger center bore required to accommodate the camera going through the spare — and the need for a tire carrier solution that will manage a 37” spare.)

I look forward to watching your build. You’ll be paving the way for the folks who follow with the 392. New models always mean new challenges. You’ll be the expert 18 months from now and the journey will be fun.
great post I placed my 392 order last Tuesday I had already planed to switch out stock 33”s and run 37” KO2, and your post confirms my thoughts. I currently run Yokohama M/T’s with 17” 8.5 Nomad rims on my 2019 Rubi. I plan on switching the Nomads over also to the 392. I’m concerned the 392 rims are too narrow plus when I have run Jeep stock rims with larger tires and any kind of lift I’ve had to use back Spacers which is a big no on this build. Another benefit of the KO2’s and Nomads they are 10lbs each lighter then 37” M/T and the 392 rims, less weight on those 392 axles
First, a 2” Mopar lift resulting in only a 1” height increase seems unlikely. The 392 will be heavier, but the Jeep should be built/sprung accordingly, so I doubt the effect of the lift will be fully cut in half.

There’s also significant risk of misinformation braided into the hype of any new model. The salesman who sold my brother his Jeep told him that Rubicon’s ”come stock with the factory lift” which, of course, they don’t. You need to really dig to get the details on the OEM suspension and lift, if any.

If no rub on full flex is the objective, the safest path is 35s. On the other hand, if you prefer the look, feel, and function of 37s, and you’re willing to pony up for a bigger lift if it’s necessary, go for the 37s and see what happens.

If the stock fit is too tight there will eventually be a good lift solution that allows full flex and good handling with 37s. If that’s what you really want, doing it up front is a lot cheaper than doing it incrementally over time.

If you’re thinking about 37” KO2s, they’re more like small 36s, so they’ll give you a little margin if you’re uncertain. They’ve been a good tire for me. The downside is poor performance in deep mud and a propensity to hydroplane on standing water. (The new studded 37” Grabbers I just mounted up as snow tires are taller with the Jeep sitting on them than my KO2s are unweighted.)

Finally, you definitely don’t want rims over 10”. A 9” rim/wheel will run the tires you’re considering, and there are a lot of 9” options with a -12 offset. (Also, remember the larger center bore required to accommodate the camera going through the spare — and the need for a tire carrier solution that will manage a 37” spare.)

I look forward to watching your build. You’ll be paving the way for the folks who follow with the 392. New models always mean new challenges. You’ll be the expert 18 months from now and the journey will be fun.
 

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BCMgunner

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Those Nomad rims sound very interesting. What is your experience with the Nomad rims? Have you used the quick deflator function? How low have you run the PSI on them?

Still waiting to hear the backspacing of the 392 rims
 

Willy's Commando

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We really don't know yet.

I was surprised by some of the differences with the diesel Wrangler. The engine is much heavier than the ones used in the gas models, so FCA had to make adjustments. The diesel Rubicon has a different suspension from the gas. As a result 37 tires fit without a lift.

Many of the standard mods that work on the gas Wranglers won't fit properly on the diesel. For example, it took a while for the after market companies to bring diesel specific lift kits to market.

I would expect FCA to make adjustments with the 392 to compensate for the size/weight of the new engine. IMHO we just have to wait and see.



I run the nomads and the 2.1 falcons 3.5” Tereflex Ailpine lift no problems with the 2.1 falcons. I wanted the diesal bad but hadn’t came out yet when I ordered my 2019 Rubi. I did place a order for a 392 last Tuesday plan on switching out to the nomads and new ko2’s the nomads and ko2’s will be a little less weight on those 392 axles only time will tell.
Jeep Wrangler JL Tire Size? EC2326B6-5431-462C-9B53-DBD7A292324B
 

Rosco P

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The concepts wheels definitely had more backspacing than the blue ore-production model with the 33s. They look just like the stock rubicon’s offset.
 

pnut

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Good discussion. I bet most people who are getting 392's are weighing their options.
I am considering 2 options, depend on what I see others do in the first few weeks:

1) Nitto Trail Grapplers in 35x11.50x17 on the stock wheels (the same exact tires on the graphite intro vehicle in all the videos). No lift, no re-gear, low-ish stress on driveline, no rubbing. This is the smartest solution, but the 37's just look so great on the JL, I am also considering:

2) 37x12.50 on aftermarket 8.5"ish wheels with less backspacing than stock. Big question is if a lift will be required, and just as important, do I think the beefed up D44's can handle this. Also gearing. I know with 470HP it won't be necessary like it would be with a V6, but still would re-gear (I do dunes every weekend).

I ordered my Graphite 392 (Half doors, and sky top) on Nov 19th.
 

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392 firecrker

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All great info! I was also trying to decide between the "smartest" choice and the "fun" choice. I went ahead and ordered Raceline Monsters (17x9) and Ridge Grapplers (37x12.5x17), because... YOLO (as my kid says). The Raceline Monsters have 4.5" of backpsacing so I am hopeful that they do not rub. Now the hard part, waiting!
 

BCMgunner

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FWIW: There is video on the interweb of a car reviewer driving the 392 concept on 37” KM2s and he chirps the tires with partial throttle from a stand still. This thing has power, and very likely enough to do whatever you’d want on heavy 37’s. Interesting that I cant find the video anymore. Maybe someone else can 🤷🏻‍♂️
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