35" to 37" considerations

[jadmt]

The exhaust will also give you ground clearance so the suitcase you are dragging under the jeep stops hitting shit.

strangely enough I have never hit my muffler on any of my jeeps...that said next time out i will probably smash it....

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[gato]

What lift and wheels do you have. i went to 37s with the OEM XR wheels, and RK 3.5” lift, and despite a fender chop and higher clearance inner fender liners my back tires rubbed the rear inner fenders with any offroad articulation, and the front tires rubbed the front lower control arms at full lock. Not my first choice but I’m running wheel spacers for now. My Jeep came stock with 4.56 gears so no issue there.

That is a RK problem. They are lazy and seem incapable of engineering the same bend that every JL front LCA from every other manufacturer has. As a result, their lifts require ridiculous amounts of backspacing, which in turn increases scrub radius, bearing and axle loads.

Pushing tires (specially front tires) further out is bad news and RK forces you to do that more than any other company.

 

[F4Flyer]

Yeah, but in his case, it is the rear tires that are rubbing. My JLURX has the stock KO2 35 which probably measure 33.5. I wonder if I can get away with the KO2 37s that measure 35.5" or so. I may need aftermarket wheels though.

 

[Terrymo]

That is a RK problem. They are lazy and seem incapable of engineering the same bend that every JL front LCA from every other manufacturer has. As a result, their lifts require ridiculous amounts of backspacing, which in turn increases scrub radius, bearing and axle loads.

Pushing tires (specially front tires) further out is bad news and RK forces you to do that more than any other company.

The spacers were to temporarily resolve the rear tires from constantly rubbing the rear inner fender liners offroad under articulation. New wheels are in my future. Your dislike of RK is duly noted.
Adjustments to the steering stops resolved the front

 

[AVGeek99]

strangely enough I have never hit my muffler on any of my jeeps...that said next time out i will probably smash it....

I'm also pretty certain I've never hit my muffler. But after my first couple trips to Moab (stock height) the tail pipe opening was no where near round.

 

[Richard_JL]

The 2020 JLUR I purchased last summer came with BFG KO2s 35x12.5x17 riding on a 3" lift. They are wearing down and later this year will need replaced. I am considering going with Mickey Thompson Baja Boss EXPs in a 37x12.5.17. The weight difference is only 2lbs per tire. I would be going from an E rated to a C rated tire. Weight being very similar, the drive train being 4.10 & 4.10 and the engine being the 2.0L (tuned) what other aspects of this larger tire upgrade should I consider?

Weight diff is not 2lbs, its 10lbs per tire. You may have been comparing 35 to 35.

 

[gato]

The spacers were to temporarily resolve the rear tires from constantly rubbing the rear inner fender liners offroad under articulation. New wheels are in my future. Your dislike of RK is duly noted.
Adjustments to the steering stops resolved the front

Actually, I don't dislike them. Their stuff is good if you are going to go with the ridiculous 4.5, 3.5" back spaces of the JK era, or will built a rock crawler beast.

They simply should offer a front lower control arm option with the conventional lateral bend for those who want to keep their tires tucked in, their rigs legal, and their scrub radius in check.

Metalcloak achieves the same articulation as RK, without forcing buyers to push their wheels out. If RK offered that front LCA, they'd be just about perfect.

 

[scorpionsix]

Weight diff is not 2lbs, its 10lbs per tire. You may have been comparing 35 to 35.

My 35s are E rated and the 37s I was looking at are C rated. Different brands as well. I will say that I'm going by published information. Is reality different? I don't actually know.

 

[Richard_JL]

My 35s are E rated and the 37s I was looking at are C rated. Different brands as well. I will say that I'm going by published information. Is reality different? I don't actually know.

There is about a 1-2 LB difference per any offroad tire depending on load range (C,D or E), so it's not a huge diff. The rubber and steel mass difference between 35 and 37" makes the bulk of the increase.

My research shows a bigger diff (~18lbs per wheel)...
BFGoodrich KO2 – 35" (LT315/70R17) Typical weight: ≈ 62–63 lbs
Mickey Thompson Baja Boss EXP – 37x12.50R17 Typical weight: ≈ 79–81 lbs

Anyway, its noticeable and 4.10 gearing may need to be lowered to make that weight 'disappear'.

 

[Cips]

Make sure your spare tire carrier can handle the extra weight and size.

 

[JeepinPete]

I appreciate your input. I really wish I could find a true 35" tire when mounted. These KO2s are coming in at 33.25". They have a decent amount of tread so probably 33.50-33.75 new when mounted.

Then go with a 37" KO2. They measure around 35.75, give or take.

 

[LSJKU]

strangely enough I have never hit my muffler on any of my jeeps...that said next time out i will probably smash it....

I eliminated that possibility the moment I drove my new '25 into the driveway. I replaced the 35+ lbs stock muffler with a 5-lbs straight pipe from MBRP that I already had. Not necessarily thinking ahead to "smashing" the muffler, but to get at least some exhaust sound and make shifting the 6spd a more audio-based thing. It worked out great.

That said, I cannot wait to get 37s mounted. With 4.88s and 35s, first gear is basically useless on the road. But it IS a hoot offroad, crawling around at less than 1mph.

 

[jadmt]

There is about a 1-2 LB difference per any offroad tire depending on load range (C,D or E), so it's not a huge diff. The rubber and steel mass difference between 35 and 37" makes the bulk of the increase.

My research shows a bigger diff (~18lbs per wheel)...
BFGoodrich KO2 – 35" (LT315/70R17) Typical weight: ≈ 62–63 lbs
Mickey Thompson Baja Boss EXP – 37x12.50R17 Typical weight: ≈ 79–81 lbs

Anyway, its noticeable and 4.10 gearing may need to be lowered to make that weight 'disappear'.

he EXP in 37 is actually 70lbs per mickey thompson...they are lighter and run on the small size. the ko2 in 35 E is 66.7lbs according to bfg.

 

[scorpionsix]

he EXP in 37 is actually 70lbs per mickey thompson...they are lighter and run on the small size. the ko2 in 35 E is 66.7lbs according to bfg.

The numbers you show are similar to what I found, seems each site may vary slightly but either way, those two tires are close in weight but 2" (or so) different in diameter. I have time to decide but may just stick with 35s and actually end up with a lighter tire if I go with the EXPs, which is definitely not a bad thing.

 

[LSJKU]

My 35s are E rated and the 37s I was looking at are C rated. Different brands as well. I will say that I'm going by published information. Is reality different? I don't actually know.

I currently run 35" KM3s, load range E @ 32psi. I've also had load range C's (different brand) that I ran at 36psi. Both performed well. With branded tires being made with modern materials and less ply's these days, the whole load range argument goes out the window in favor of the Load Index rating. You will be happy with either, just run the appropriate air pressure.

Oh geez, please forgive me, I hope I didn't just provoke another "Load Range" debate!!!

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