Tire height vs axle strength

[ExitLeft]

So....I keep reading all these posts and seeing all these pictures of Rubicons on 35s, 37s, 38s, and even 40s and I can't help but wonder how well these new Rubi axles are holding up. I know the JL axles are stronger than the JK axles. It was common knowledge that you were "OK" with up to a 35" tire on a JK. I ran 34" tires (285/75-17 Ridge Grappplers) on my JKUR and was mildly concerned about it. Especially after I had to replace a leaking axle seal.
Now with the JL, are you guys running 37s having any issues? I saw one youtube video where someone on 37s destroyed either a U-Joint or a ball joint while rock crawling. But other than that one failure I've not seen anything.
I have a 2019 JLU Rubicon on order and plan on putting those same 34" tires on it without a lift. But, of course, I'm also thinking of a 2.5" - 3.5" lift and 35s or 37s. so it got me thinking...

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[chevymitchell]

It's all about controlling your throttle. You're not going to hurt your axles with 37's as long as you drive/wheel like you have some sense.

 

[tCub]

It's all about controlling your throttle. You're not going to hurt your axles with 37's as long as you drive/wheel like you have some sense.

Interested in this too. And I appreciate your response, chevymitchell, but do you have any additional technical response to add?

What I’m wondering specifically is are 35” tires okay for a Sport S with standard M186/M200 axels? And for the OP, a Rubi with even larger 37+?

I see people here and elsewhere showing off massive tires (even on Sport/Sahara) and perhaps they’ll never have an issue but they may also never wheel...

For me, I’m going once a month. Terrain ranges from grassy, to gravel, to mud to rocks.. nothing really extreme but as my skill progresses and when I get larger tires, I want to make sure I’m not setting myself up for breaking something really important.

Do incidents like broken U joints and trashed axels really happen more due to “bad” wheeling than anything else?

 

[chevymitchell]

Interested in this too. And I appreciate your response, chevymitchell, but do you have any additional technical response to add?

What I’m wondering specifically is are 35” tires okay for a Sport S with standard M186/M200 axels? And for the OP, a Rubi with even larger 37+?

I see people here and elsewhere showing off massive tires (even on Sport/Sahara) and perhaps they’ll never have an issue but they may also never wheel...

For me, I’m going once a month. Terrain ranges from grassy, to gravel, to mud to rocks.. nothing really extreme but as my skill progresses and when I get larger tires, I want to make sure I’m not setting myself up for breaking something really important.

Do incidents like broken U joints and trashed axels really happen more due to “bad” wheeling than anything else?

This particular question has been addressed many times in other threads, but to sum it up, it's all about torque. Torque is linear from the engine through the transmission, transfer case, differentials and then finally to the tread of the tire.

If you go to a larger tire, in order to maintain the same linear tq through the drivetrain, you would have to compensate with gearing. Eventually, you would reach a point where you'll have structural failures in things like you mentioned, u-joints, axle shafts...

There's a bunch of fancy math I could show you here, but there are other threads with that math included.

You would be fine with 35's on your non-Rubicon. You could always re-gear to compensate for the 4LO 1st gear in that transfer case to crawl as slow as possible. Slower the better and you don't break things that way. These new Rubicon axles will be able to handle a 37 without issue. That's what I'll be running, myself.

There really isn't enough real world data to support an opinion one way or the other right now, however, you can do the math and that will tell you.

Keep in mind, there are guys who have run a 35 on the little Dana 30 on the XJ without issues for years and years. If you wheel smartly, you won't have an issue. Daily driving definitely won't be a problem. You'll just notice the normal things like, slower acceleration and lower MPG's.

I just got my Rubicon back home from a several month long road trip and wheeled Colorado, MOAB, and Big Bear with zero issues. All I did was put gas in it, change the oil, and rotate tires. She's banged up pretty good underneath, but no issues at all. (Stock JL).

 

[tCub]

Thanks for not being a huge dickhead and leaving your response at “this question has been asked before” - not sarcasm either - I’m really appreciative of your thorough response. You see, sometimes, you don’t know what you don’t know. I’ve definitely searched these forums and online and YouTube for an answer to this question but perhaps my query was too specific. You getting to the heat of the meat of the issue (torque, XJs on 35s with Dana 30s) and interjecting your own experience gives me leads to search in other terms to find my answer and better understand how my Jeep works.

Not to stray off topic.. it’s just refreshing to get a non-douchebag response.

Happy wheeling!

 

[ExitLeft]

As the OP, I thank you for your responses. as @chevymitchell said, time will tell on the new JL axles. I'm not an aggressive off-roader, but my JKU (soon to be JLU) is my daily driver and I go offroad about once a month. With my JKUR I typically just put it in 1st or 2nd while in 4-LO and crawl. I'll start with the same 34's I have and by the time they wear out I'm sure there will be enough experience of JL's on 37's to help me make a choice. I know the JL is a different animal, but I just can't get over the fact that people put 37s on a stock JL axle and wheel it without trusses/braces, etc. It's a good time to own a JEEP!

 

[Litfuse]

As the OP, I thank you for your responses. as @chevymitchell said, time will tell on the new JL axles. I'm not an aggressive off-roader, but my JKU (soon to be JLU) is my daily driver and I go offroad about once a month. With my JKUR I typically just put it in 1st or 2nd while in 4-LO and crawl. I'll start with the same 34's I have and by the time they wear out I'm sure there will be enough experience of JL's on 37's to help me make a choice. I know the JL is a different animal, but I just can't get over the fact that people put 37s on a stock JL axle and wheel it without trusses/braces, etc. It's a good time to own a JEEP!

I agree! When I use to wheel often over ten years ago with TJs and YJs, we would often run 37-38.5 inch tires. We would always have dana 60s as axles or at least a HP44 in the front. I saw a lot of Dana 30s and 35s explode.

 

[BostonJohn13]

I was recently watching Ultimate Adventure and saw Dana was running a JL with 37s. It looks like the same Advantek D44 on the Rubi's and no mention of axle mods other than regearing.

If Dana is comfortable running 37s on this setup, hopefully that means the axles are engineered to handle it. Who knows, time will tell.

http://www.fourwheeler.com/ultimate-adventure/2018/1807-sponsors-of-ultimate-adventure-2018/

 

[intentsrig]

Guess he was going pretty hard on it. Must have been. I read it was an uphill section full of rocks. I think the tire he was running was 38x13.50

 

[ChattVol]

This particular question has been addressed many times in other threads, but to sum it up, it's all about torque. Torque is linear from the engine through the transmission, transfer case, differentials and then finally to the tread of the tire.

If you go to a larger tire, in order to maintain the same linear tq through the drivetrain, you would have to compensate with gearing. Eventually, you would reach a point where you'll have structural failures in things like you mentioned, u-joints, axle shafts...

There's a bunch of fancy math I could show you here, but there are other threads with that math included.

You would be fine with 35's on your non-Rubicon. You could always re-gear to compensate for the 4LO 1st gear in that transfer case to crawl as slow as possible. Slower the better and you don't break things that way. These new Rubicon axles will be able to handle a 37 without issue. That's what I'll be running, myself.

There really isn't enough real world data to support an opinion one way or the other right now, however, you can do the math and that will tell you.

Keep in mind, there are guys who have run a 35 on the little Dana 30 on the XJ without issues for years and years. If you wheel smartly, you won't have an issue. Daily driving definitely won't be a problem. You'll just notice the normal things like, slower acceleration and lower MPG's.

I just got my Rubicon back home from a several month long road trip and wheeled Colorado, MOAB, and Big Bear with zero issues. All I did was put gas in it, change the oil, and rotate tires. She's banged up pretty good underneath, but no issues at all. (Stock JL).

Thanks for the informative reply...your input is greatly appreciated. It's good to hear you see alot of folks having no issues wheeling 35" tires on the jl d35 & d30 axles. I'm offroading(rutted trails/some rocks/moderate climbs) once/twice month with my daily driver(25k miles/yr) 6 speed jlus with 3.45 gearing and d30 front and d35 rear axles(wish I would've upgraded to d44 rear with limited slip). I added rubi takeoff suspension/wheels/tires and want to add 2" spacer lift/shock extensions with 315/70/17 ko2 class c to preserve on road ride quality and mpg's while adding clearance. Going from 31" stock highway tires to 33" rubicon ko2, I dont get to use 6th gear as much I use to with 31" tires.(can only use when going 75+mph on flat or downhill hwy travel) Would a jlus meaningfully gain mpg/acceleration/better crawling by spending $1200 to go to 4.10 gearing when you go to 315/70/17 tires?

I'd also like to add front & rear lockers when reasonably priced lockers($2-300 range) are available. I cant justify spending $900+/each locker for ARB air lockers. I assume it would make sense to regear and add lockers at same time? Is it wishful thinking to regear and add lockers with labor for $2k or less? I'd also greatly appreciate @TTEChris opinion as he is also a wealth of knowledge!

Please go easy with the "you should have bought a rubicon" comments, because I know this and fully agree! However, I got my sport s for $4200 below msrp which was $8k less than a similiar rubi.(wife would've killed me if I spent $41k on a jeep)

 

[ChattVol]

@Sheepjeep any thoughts on post above is appreciated!

 

[Sheepjeep]

@Sheepjeep any thoughts on post above is appreciated!

Don't know how I got roped into this but here is my 2 cents


Like said the JL axles of all sizes are still new to really know what the main week points are, yes you can get an idea of strength by looking at shopping counts and sizes of joints and others parts.


Driving style has a huge impact on the life of the axles. You want to rock bouncer stuff on stock axles locked with 40s that will get expensive fast. But driving around town like that not so bad minus ball joints. Also keep in mind bigger tires mean harder trail which means more skinny pedal so high chance of brakage.


I wheeled for years I wheeled 37x13.5 tires on a built waggy dana 44 and ford 8.8 which is pushing it's limits, but driving smart never really broke anything. You stay to get bound up, stop. I have been seen plenty of 60s on 37s blow up due driving thinking they are invincible.


From that photo thought not knowing what happened but it looks like I keep the tube took a really good hit at the fad which caused the tube to break probably a cracked fad casting. This is not the larger the allowing the Jeep to go on more aggressive trails than the failure being a direct result of the tire size causing the problem.

 

[Zandcwhite]

A picture of one broken fad, which has a giant witness mark at the point of failure, doesn’t mean much. We have all seen videos of rock bouncers snapping Dana 80 housings. Impacts and shock loading will break anything if they are severe enough. If you want to jump your Jeep, truss it regardless of tire size. If you want to do full throttle assaults in Boulder fields, upgrade your axles. Even in the Jeep world, speed costs money. Slow and moderate, back up, stack rocks, or winch when needed, and the rubi axles will live a long life on 37’s. Wheel smart on stock axles or upgrade if you want to bash your way through terrain. I wouldn’t trust the stock axles on stock tires trying to rock bounce through little sluice (not to mention I wouldn’t bash the rest of the shiny new Jeep that way).

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