35" to 37" considerations

[scorpionsix]

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?

Sponsored

 

[jadmt]

I have a 3.6 with 4.10's and went from 35's to 37's both Mickey thompson bb at and I was worried I would need to re-gear but so far it has done great..been to moab no issues..I was more worried on the highway but seat of the pants it is no different..I see 6, 7th and 8th gears...plenty of giddy up. you should be better as the 2.0 has more pep than the 3.6. I live in Montana so either up or down but I see you are in denver so you hare a bit higher elevation so that might come into play..altho I was in the san juan area doing the normal trails with no issues and the highway driving was not a problem and there os a bit of elevation around ouray silverton etc.

 

[Tr4ckD4ys]

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?

What do you mean by tuned? Tuning the engine doesn’t change weight or revolutions of the tire, it only increases the wear you’re putting on your drivetrain components because of carrying that weight/revolutions around at more boost/load %.

Depending on the actual tire and other vehicle mods, everyone’s experience can be drastically different.

 

[scorpionsix]

- what do you mean by tuned? Tuning the engine doesn’t change weight or revolutions of the tire, it only increases the wear you’re putting on your drivetrain components because of carrying that weight/revolutions around at more boost/load %. So this isn’t necessarily a good work around.
- 4.10, in my personal opinion, is too low for 37s. The factory 4.56 is borderline acceptable. You won’t see much of 8th gear anymore once you install and you will feel less powerful in 7th.
- E to C rated is fine. Will probably ride a bit better but have (marginally) less sturdiness off-road.

depending on the actual tire and other vehicle mods, everyone’s experience can be drastically different.

By tuned, I mean a SuperChips tune combined with CAI and cat back exhaust. I mentioned that because I don't think my ride will be under powered or under geared with 4.10s running 37s and a moderately tuned 2.0L. I am thinking about any possible additional stress to the suspension going with the taller (fortunately not heavier) tires. I'm not a suspension or geometry specialist so I simply don't know which is why I posted.

 

[Terrymo]

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.

 

[Tr4ckD4ys]

By tuned, I mean a SuperChips tune combined with CAI and cat back exhaust. I mentioned that because I don't think my ride will be under powered or under geared with 4.10s running 37s and a moderately tuned 2.0L. I am thinking about any possible additional stress to the suspension going with the taller (fortunately not heavier) tires. I'm not a suspension or geometry specialist so I simply don't know which is why I posted.

Taller tire = more load % needed to move the vehicle
More load % = more boost requested by ECU
More boost provided = more wear on drivetrain

Your tune is only multiplying that effect. While it may feel like you have the power to move the tires (you most likely do!), doing so on 37s versus on 35s increases the demand on the vehicle. I’m not saying this is bad or wrong. It’s totally subjective (I’m in the exact same boat as you). But it’s something you have to be aware of. Now I am doing this on 4.56 gears and I don’t like how much forth and back there is between 7th and 8th gear on the interstate.

What works for one person may not work for the next. Either way, running 37s at 4.10 with a tune is not something I’d recommend. I would just feel all the time like I’m running my vehicle on borrowed time.

 

[kah.mun.rah]

It will feel very similar your 35s but you will have a better experience with the hills and mountains in CO with a re-gear. Other than that, you might have to invest in a different tire carrier to clear your bumper with the spare. 3" is enough lift so no need to modify your current suspension. Also as mentioned above, the offset of your wheels will determine if you rub or not when turning. If you are running 35s I assume that you have a programmer already. If not, add that to your list.

 

[scorpionsix]

Taller tire = more load % needed to move the vehicle
More load % = more boost requested by ECU
More boost provided = more wear on drivetrain

Your tune is only multiplying that effect. While it may feel like you have the power to move the tires (you most likely do!), doing so on 37s versus on 35s increases the demand on the vehicle. I’m not saying this is bad or wrong. It’s totally subjective (I’m in the exact same boat as you). But it’s something you have to be aware of. Now I am doing this on 4.56 gears and I don’t like how much forth and back there is between 7th and 8th gear on the interstate.

What works for one person may not work for the next. Either way, running 37s at 4.10 with a tune is not something I’d recommend. I would just feel all the time like I’m running my vehicle on borrowed time.

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.

 

[scorpionsix]

It will feel very similar your 35s but you will have a better experience with the hills and mountains in CO with a re-gear. Other than that, you might have to invest in a different tire carrier to clear your bumper with the spare. 3" is enough lift so no need to modify your current suspension. Also as mentioned above, the offset of your wheels will determine if you rub or not when turning. If you are running 35s I assume that you have a programmer already. If not, add that to your list.

I have the Super Chips programmer/tuner and punched in 33.25" measured then tested against a speedo app. I was within 0-1 MPH of the digital speedo and the app. Good enough for gov't work : )

 

[Tr4ckD4ys]

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.

Well … at the end of the day you want to enjoy your vehicle so I say fu** it and put those 37s on. If you have problems you can always try to sell them and go back to 35, or consider the regear.

 

[Grey24Rubi]

37's just make everything more better'er

 

[scorpionsix]

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.

Not sure what springs were used but the shocks are Fox. Not sure which model but no reservoir so probably entry level 2.0

 

[jellis4148]

A CAI, and cat back exhaust will do nothing but make your wallet weight less. They are a complete waste of money, unless you just like the sound.

 

[yokramer]

A CAI, and cat back exhaust will do nothing but make your wallet weight less. They are a complete waste of money, unless you just like the sound.

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

 

[scorpionsix]

A CAI, and cat back exhaust will do nothing but make your wallet weight less. They are a complete waste of money, unless you just like the sound.

Irrelevant to this thread but since you made your statement, I'll tell you that you are wrong. The improvements are negligible on their own and definitely singularly. But combined and with a tune that is able to take advantage of such upgrades, they do in fact make a difference. Not necessarily on a dyno but throttle improvement is what I was after and achieved.

Sponsored