JLURD considerations - moving from 37x12.5x17 tires to 38 or 39x13.5x17

[JL_Wildlife]

Regear is a pure highway optimization. With the 4:1 xfer case and an automatic, you've got plenty of torque. Gears make torque. My 2.0 T that doesn't make as much torque as the diesel, easily climbs vertical with stock gears & 37's in M1 @ 1,200 RPM.


a km3 37 isnt really a 37, it's 35-36 per memory.
Mine measured 35 13/16"

Glad to hear that! Good to know. Thanks!

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[drick]

a km3 37 isnt really a 37, it's 35-36 per memory.
Mine measured 35 13/16"

so then if we assume the 39's follow suit - then I'm basically getting a 38, right? if so, this is why I'm less concerned about moving up to the 39 in a BFG.

now the 12.5->13.5 is still something i need to think about based on current rim and backspacing.

 

[OBJLU]

so then if we assume the 39's follow suit - then I'm basically getting a 38, right? if so, this is why I'm less concerned about moving up to the 39 in a BFG.

now the 12.5->13.5 is still something i need to think about based on current rim and backspacing.

Lol a 37 really when brand new

 

[drick]

Lol a 37 really when brand new

i rounded up as he had the 13/16 shown and clearly has done the comparison...

 

[Rangemaster]

i rounded up as he had the 13/16 shown and clearly has done the comparison...

I will be moving to 38” once I get the following done in the months ahead. I have all the parts, just waiting for time and downtime to do all the work.

Fender chop & inner fenders
RCV axles
Knuckles
Ball Joints
Truss kit
Bump stops
One ton tie rods
4:10 gears
Diff Covers & oil change

Man, now that I just listed all the parts. I should have went 1 tons and sell the stock axles.

 

[drick]

so then if we assume the 39's follow suit - then I'm basically getting a 38, right? if so, this is why I'm less concerned about moving up to the 39 in a BFG.

now the 12.5->13.5 is still something i need to think about based on current rim and backspacing.

FWIW - talked to shop about this earlier in the week. he doesn't think the extra weight of 39's or the extra height and width should make any material difference in the build.

i'm going to wait for the RCV's to come i think just to be safe and do these both at the same time.

 

[drick]

I will be moving to 38” once I get the following done in the months ahead. I have all the parts, just waiting for time and downtime to do all the work.

Fender chop & inner fenders
RCV axles
Knuckles
Ball Joints
Truss kit
Bump stops
One ton tie rods
4:10 gears
Diff Covers & oil change

Man, now that I just listed all the parts. I should have went 1 tons and sell the stock axles.

then you wouldn't have anything to look forward to later...

 

[kah.mun.rah]

IMO 12.5 on 37s starts to look pretty skinny so a 12.5 on a 38 or 39 would look like pizza cutters.

 

[drick]

IMO 12.5 on 37s starts to look pretty skinny so a 12.5 on a 38 or 39 would look like pizza cutters.

i have them on both rigs right now, and i never had that thought on the jk. for the jl, i don't disagree - it seems that i have a lot more "white space" - even when i put them right next to each other.

on the other hand, if they look awesome but rub or mess up my suspension - then that would suck and set me back.

 

[Atom631]

Regear is a pure highway optimization. With the 4:1 xfer case and an automatic, you've got plenty of torque. Gears make torque. My 2.0 T that doesn't make as much torque as the diesel, easily climbs vertical with stock gears & 37's in M1 @ 1,200 RPM.


a km3 37 isnt really a 37, it's 35-36 per memory.
Mine measured 35 13/16"

no tire on the market will measure true when its under the jeep. My 38” Ridge Grappler measures 36.5” under my jeep at 30psi. off the jeep it measures almost exactly its advertised size (37.76”).

 

[Atom631]

IMO 12.5 on 37s starts to look pretty skinny so a 12.5 on a 38 or 39 would look like pizza cutters.

38x12.50 Ridge Grapplers

 

[Jtclayton612]

FWIW - talked to shop about this earlier in the week. he doesn't think the extra weight of 39's or the extra height and width should make any material difference in the build.

i'm going to wait for the RCV's to come i think just to be safe and do these both at the same time.

For full flex I think you’ll need to do a little body trimming in the rear wheels with the bfg 39s but I’m not 100% sure.

 

[Kaliks&Bones]

38x12.50 Ridge Grapplers

Any profile shots you can add?

Those look great staring down the barrel though!

 

[Atom631]

Any profile shots you can add?

Those look great staring down the barrel though!

this on a 2.5” RK lift and Bushwacker Hyperform highline fenders. waiting for my spare to come in.

 

[J0E]

no tire on the market will measure true when its under the jeep. My 38” Ridge Grappler measures 36.5” under my jeep at 30psi. off the jeep it measures almost exactly its advertised size (37.76”).

True, but at 36 PSI, which the tires were inflated, they drop .05". See BT39.com
Also measured at 0 PSI before I had them mounted.

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