Mods required to run 37" tires on 2dr Rubicon 3.6

bfschor

bfschor

New member
Ok, I'm joining this a little late, but had been thinking about this subject for a while now. I'm running Duratracs advertised as "35" inch tires, which we all know aren't. I think they're actually closer to a small 34" or big 33". I've read in countless posts that not all tires are true to their advertised size - even 37's are more closer to an actual 35", maybe 36". But those that run 35's seem to complain a lot that they're not actual 35 inches. So I guess what I'm asking is, if tires were sized exactly as advertised, wouldn't those of us that run 35's have to do the same prep work that we're talking about in this thread when running 37's? And why aren't tire sizes more accurate anyway??
 
2nd.gunman

2nd.gunman

Caught the Bug
bfschor said:
Ok, I'm joining this a little late, but had been thinking about this subject for a while now. I'm running Duratracs advertised as "35" inch tires, which we all know aren't. I think they're actually closer to a small 34" or big 33". I've read in countless posts that not all tires are true to their advertised size - even 37's are more closer to an actual 35", maybe 36". But those that run 35's seem to complain a lot that they're not actual 35 inches. So I guess what I'm asking is, if tires were sized exactly as advertised, wouldn't those of us that run 35's have to do the same prep work that we're talking about in this thread when running 37's? And why aren't tire sizes more accurate anyway??
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Check out the tire size thread. Every tire runs smaller than advertised but anywhere people are talking what will fit or needs to be done for a certain tire size they are always referring to ADVERTISED size not actual size.

Only time actual size is worth worrying about is when comparing brands with the same advertised size.
 
JoeB-JKURX

JoeB-JKURX

New member
Induced Torque

MedixJK said:
True but the induced torque on drive line components is day and night compared to 37s
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A 37 (if at the advertised size) will induce 5.7% more torque than a 35 (it is the ratio of the radiuses) compared to 9.3% in going from 32s to 35s. It is also true, however, that 37s weigh more than 35s and, therefore put more load on the drive train. I'd expect there is straw breaking a camel's back in there somewhere. I was wheeling today (pretty hard, not extreme, rock crawling trails) with a fellow that had a 2013 Rubicon and 4.10 gears (gusseted stock axles and shafts) with 37s. He didn't break anything today.
 
MedixJK

MedixJK

-
JoeB-JKURX said:
A 37 (if at the advertised size) will induce 5.7% more torque than a 35 (it is the ratio of the radiuses) compared to 9.3% in going from 32s to 35s. It is also true, however, that 37s weigh more than 35s and, therefore put more load on the drive train. I'd expect there is straw breaking a camel's back in there somewhere. I was wheeling today (pretty hard, not extreme, rock crawling trails) with a fellow that had a 2013 Rubicon and 4.10 gears (gusseted stock axles and shafts) with 37s. He didn't break anything today.
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Its not black and white for sure. The gray area is much bigger with 37s i feel like. I had a buddy running same setup, d44, 4:10, 37s, snap a rear shaft. He had wheel spin on a ledge, tires decided to bite and pow. Its all situation. You just start to get where the odds arent nearly as favorable for you.
 
littlered_jk

littlered_jk

Member
MedixJK said:
Its not black and white for sure. The gray area is much bigger with 37s i feel like. I had a buddy running same setup, d44, 4:10, 37s, snap a rear shaft. He had wheel spin on a ledge, tires decided to bite and pow. Its all situation. You just start to get where the odds arent nearly as favorable for you.
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Yeah I've heard of people even snapping their shafts with stock tires in those same situations.
 
Draconianwinter

Draconianwinter

New member
MedixJK said:
Its not black and white for sure. The gray area is much bigger with 37s i feel like. I had a buddy running same setup, d44, 4:10, 37s, snap a rear shaft. He had wheel spin on a ledge, tires decided to bite and pow. Its all situation. You just start to get where the odds arent nearly as favorable for you.
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littlered_jk said:
Yeah I've heard of people even snapping their shafts with stock tires in those same situations.
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Yeah axles and differentials are very much alike in the fact they don't like being shock loaded

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desertrunner

desertrunner

Active Member
just my :twocents: on the 37s, I ran 37 KM2s on my 08 Rubi unlimited, stock rubi axles, 4.10s in Colorado. I was a bit careful off roading i didnt mash the skinny peddle to much to get up ledges and such and i managed not to break any shafts or R&P. I had C gussets and front axle sleeves (sleeves are most likely a waste of money as most on here will agree) with the 4.10s and the 4-1 T case it did pretty well on the rocks but i did have to ride the clutch a bit on the big stuff. I will say though going up Vail pass was a kick in the balls in 3rd gear RPM up pretty high just to not get passed my Semi trucks haha so a Re gear would have been really nice but i never got around to doing it. But i would For sure recommend new ball joints, by the time i got around to replacing them my stock ones pretty much fell apart in my hand they were so shot. And my stock E lockers managed to work fine with the 37s but eventually may wear out as many have seen one here

I had a 4dr with heavy rear bumper and then a stubby stinger and vr8k winch up front and i thought my RK3.5" kit was the perfect height with stock cut fenders so depending on weight 2.5 on the 2 door might work out well / maybe slightly low. I also had the 37s mounted on procomp steel rims so may have been a little heavier than on alloy rims
 
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littlered_jk

littlered_jk

Member
desertrunner said:
just my :twocents: on the 37s, I ran 37 KM2s on my 08 Rubi unlimited, stock rubi axles, 4.10s in Colorado. I was a bit careful off roading i didnt mash the skinny peddle to much to get up ledges and such and i managed not to break any shafts or R&P. I had C gussets and front axle sleeves (sleeves are most likely a waste of money as most on here will agree) with the 4.10s and the 4-1 T case it did pretty well on the rocks but i did have to ride the clutch a bit on the big stuff. I will say though going up Vail pass was a kick in the balls in 3rd gear RPM up pretty high just to not get passed my Semi trucks haha so a Re gear would have been really nice but i never got around to doing it. But i would For sure recommend new ball joints, by the time i got around to replacing them my stock ones pretty much fell apart in my hand they were so shot. And my stock E lockers managed to work fine with the 37s but eventually may wear out as many have seen one here

I had a 4dr with heavy rear bumper and then a stubby stinger and vr8k winch up front and i thought my RK3.5" kit was the perfect height with stock cut fenders so depending on weight 2.5 on the 2 door might work out well / maybe slightly low. I also had the 37s mounted on procomp steel rims so may have been a little heavier than on alloy rims
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Lots of info thanks. I have the 2 door with a steel rock krawler bumper with a q9500is synthetic winch on it. Rear bumper is a 170lb steel bumper with swing out tire carrier. I'm weighing around 4600 on the scales now with my current setup. I'm leaning to the mastercraft courser MXT's. They're a lighter 37 and I have a few friends that are running them on their 4 doors and praise them. Having my lift size and flat fenders I'm thinking I'll be ok.
 
Trail Jeeps

Trail Jeeps

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A 37" tire can make the biggest obstacle that much easier, and they sure look good. But, unless you're going to go the monty: sleeve or truss, c gussets, axle shafts and gears, gears, gears, they're generally not worth it. You can get over anything with your 35 that you can with your 37 with careful driving. 35's are kind of the tipping point with these Jeeps. Rubicon 4.10s, some c gussets, a tuner and some mindful driving will still have good street manners and will be great as a daily for the life of the Jeep. 37's sort of push it over the edge. Sure, they're not THAT much bigger, don't have THAT much more rotating force, blah, blah, blah but you've crossed a threshold in functionality of the stock-ish drivetrain.

Of course people will respond saying "I LOVE my 3.73 geared Jeep on 37's" and I'm not here to argue that point, but if you want it right and get everything out of your Jeep, go all in or love your JK on 35's.
 
cozdude

cozdude

Guy with a Red 2-Door
Trail Jeeps said:
.

Of course people will respond saying "I LOVE my 3.73 geared Jeep on 37's" and I'm not here to argue that point, but if you want it right and get everything out of your Jeep, go all in or love your JK on 35's.
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And don't forget that these are the people with 3 sets of light bars on there jeeps as well cause they are more important than gears [emoji23]


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Draconianwinter

Draconianwinter

New member
Trail Jeeps said:
A 37" tire can make the biggest obstacle that much easier, and they sure look good. But, unless you're going to go the monty: sleeve or truss, c gussets, axle shafts and gears, gears, gears, they're generally not worth it. You can get over anything with your 35 that you can with your 37 with careful driving. 35's are kind of the tipping point with these Jeeps. Rubicon 4.10s, some c gussets, a tuner and some mindful driving will still have good street manners and will be great as a daily for the life of the Jeep. 37's sort of push it over the edge. Sure, they're not THAT much bigger, don't have THAT much more rotating force, blah, blah, blah but you've crossed a threshold in functionality of the stock-ish drivetrain.

Of course people will respond saying "I LOVE my 3.73 geared Jeep on 37's" and I'm not here to argue that point, but if you want it right and get everything out of your Jeep, go all in or love your JK on 35's.
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This is why it will be a couple years at least before I will run 37's. Have to be able to afford those axles from Dynatrac

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Draconianwinter

Draconianwinter

New member
Trail Jeeps said:
Dynatracs are worth every penny, but a properly dressed Rubicon 44 will hold up well with the right treatment.


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Yeah but I know me. Lol. While I tend to go slow it will be just a matter of time besides that is my dd also so can't afford to have not working. With 35s I will be able to do pretty much everything with less stress on the axle components.

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littlered_jk

littlered_jk

Member
Trail Jeeps said:
Dynatracs are worth every penny, but a properly dressed Rubicon 44 will hold up well with the right treatment.


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Yeah I'm pretty cautious with my jeep. Pick the right lines and don't floor the skinny pedal. My jk wasn't cheap when I bought it and I don't want to thrash it. Just want to have fun with it make it look good and does well off road
 
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