ready for 37s?

ok, so i was looking at my 34s with my 2.5" lift. then i got a tape measure and from the center of my wheels measured 2 inches past my 34s. know what? it's at least 4 inches from the 34s to the closest surface (rear bumper & rear pinch seam). so i got to thinking, maybe by trimming the pinch seam and maybe the rear bumper, i could fit 37s. what do you guys think? i know, the flex thing right? well i started looking at the xenon high clearance narrow flat fenders. the lip of our factory fenders is about 1.5". with flat fenders, thats 1.5" more room for flex. maybe even a 1" body lift for good measure???

so here's my math. stock i fit a 33" tire with no lift & no rubbing at full flex.
add 1.5" for flat fenders, plus 2.5" suspension lift and 1" body lift.
thats 33+1.5+2.5+1 = 38 or 37" tire and 1" extra for flex. thats the plan anyways.

i know, i know. the d30 is too "weak". well it has the same inner & outer knuckles as the d44. the big diff is the axle shafts. 27 vs 30 and bigger u-joints connecting the inner & outer shafts.

heres what i was thinking to "fix" the d30 weakness:
1) alloy usa chromolly shafts
2) stock carrier is weak (ask redneck), so an ARB locker to replace the carrier
with the stronger ARB carrier and give me a locker in the front.

along with the flat fenders and maybe a 1" body lift, do you guys think it'll work?

And what about regearing? This seems like a lot of work and cost just for 37`s. And don`t forget even with regearing, I think you`re gonna pay in the end in fuel pushing that larger tire. I`ve got room for 35`s now, and if I go with pucks, 37`s for sure. But I`m not sure a little bigger tread justifies all the costs especially with the way gas is going. I know a lot of you running larger meats say all is good, but you are using more gas with that much more rolling resistance. I myself would stick with 35`s. Not as beefy, but better on driveline, fuel, speed,shifting etc, etc. just my .02

I run 37's with a 3" FT Ultimate lift, a 1" body lift, and a very small about of cutting.

With your BB lift and Xenon flares I would not be scared to run 37's, especially with a 1" body lift, but I would think you could get by with out it. There is at least 2 people on the JK-Forum running Xenon flares and no lift clearing 36's.

You only live once. Do it.

Duke in reguards to Crux post, just curious...what kind of gas mileage do you get?

TxRubiRig wrote:

Duke in reguards to Crux post, just curious...what kind of gas mileage do you get?

thats a good question. so duke, how many mpg? are you still running the stock 4.10 gears?

adam, you've got very good points. but, like you said, not a lot of difference between 35s & 37s. with 35s, i'd be looking at the same upgrades too. i'm the "better safe than sorry" kind guy. i'd rather over build it not to break than worry about it after it does. i did forget to mention the gears, 4.88s. my math went like this.... i had 4.10s and 33s on my first jk with no issues. i figured 4.56s would be just enough for 35s and that left 4.88s should be just enough for 37s. not the best crawl ratio, but enough cajones so that my tanny isnt downshifting with the slightest beeze or slope and overdrive is useable again.

now 37s would be at least a year off. for now it would be the shafts, locker/carrier, and gears. then fenders with good xmas & birthday $$, and finally tires with my income tax (or i get over anxious and decide to sell one of my babies... the FN 308 or Rock River AR-15 )
gas is killing alot of us right now, i admit. but we have carmen's little 4-banger and we already decided to carpool more.

i figure worse case senario is i build up a bad ass axle for 35s

ok I'm gonna put my two cents in again.............

you guy's are forgetting about unsprung or rotational weight of the 37's

when you go to a larger tire like that you need to be geared right 4.88's are just not enough for 37's........not on the street at least...........you are gonna see bad gas mileage and poor performance on the highway ..........that combo is not a good mix but would be ok if your Jeep was for offroad use only.........expecially with an Automatic.


well thats my two cents

jeeperjennie wrote:

....................wrong user name...........

that was me

this is what i was saying

hahaha ................37's on a d30<---------


spend the $$$$$$ and you will still be



get a rubi axle and then upgrade that, hell its only a few hundered more dollars than the arb and compressor

hmm a geared d44 with alloys and ctm joints
rubi d44 = 1400$
alloy shafts = 800$
ctm joints = 225$

total = 2425$ <---------damn near unbreakable in a jk with 37's

me not having to fix your shit at the next trail run = priceless

TxRubiRig wrote:

Duke in reguards to Crux post, just curious...what kind of gas mileage do you get?

I don't find any real value in taking the time to calculate my mpg. I can't go any where when the gas tank is empty, so I fill it up. Also I don't drive the Jeep emough that it is a huge impact. It is a year old next week and has 3500 miles on it.

I would guess and it is just that a wild ass guess that I am getting in the neighborhood of 13-14 mpg. I do know of at least one JK on 37's that does get 18-19 mpg, but the owner has regeared, changed exhausts, changed intakes, added Hypertech chip, etc.......

jeeperjennie wrote:

ok I'm gonna put my two cents in again.............

you guy's are forgetting about unsprung or rotational weight of the 37's

when you go to a larger tire like that you need to be geared right 4.88's are just not enough for 37's........not on the street at least...........you are gonna see bad gas mileage and poor performance on the highway ..........that combo is not a good mix but would be ok if your Jeep was for offroad use only.........expecially with an Automatic......

I still have the stock 4.10 gears and have not problem on the street with the overdrive disengaged with my auto transmission. Its on the trail on the biggest ledges that I want more gearing (keeping in mind of my last 3 wheelers one had a 6.5:1 tcase and another had a doubler). On the trails like we see at Long's or Boulder deeper gearing is not a huge issue, but on the bigger stuff in Katemcy, Inks, Farmington, Moab, etc.... It is a problem.

All of that being said by the end of summer I intend to be running 5.13's and have upgraded to alloy shafts (better safe than sorry, right?).

redneckhouston wrote:

jeeperjennie wrote:

....................wrong user name...........

that was me

this is what i was saying

hahaha ................37's on a d30<---------


spend the $$$$$$ and you will still be



get a rubi axle and then upgrade that, hell its only a few hundered more dollars than the arb and compressor

hmm a geared d44 with alloys and ctm joints
rubi d44 = 1400$
alloy shafts = 800$
ctm joints = 225$

total = 2425$ <---------damn near unbreakable in a jk with 37's

me not having to fix your shit at the next trail run = priceless

I agree that the upgraded D44 would be a step in the right direction. Its only money, right?

Oh, and Richard, you already know I got dibs on the babies!!! :soldier:

I would have to agree with G, spend the grip and get the whole enchilada with the D44`s. I was just bringing up the point about fuel cuz I`m now paying about$70.00 to fill up every 2 days. Thats a lot of $$$. So on top of your upgrades, you have this to contend with. And since it`s still a daily driver, I might not build it up that much for the trail when it spends 90-95% on highway. I ran 31`s on my TJ at first, and when I upgraded to a 32, I lost approx. 50 miles per tank! Don`t get me wrong, I think 37`s would be sweet for you Richard, but I`m thinking about all the costs. I`m even looking for people selling their rubi tires and staying at 32`s. Not sure yet but if gas keeps going up, I gotta cut costs anywhere I can. Sorry to have sorta highjacked the thread.

like i said before, eveyone has good points. with gas i have to agree. i am getting about 300-320 miles per tank on my 33" ATs. with the 34" LTBs i was only getting about 240 per tank . only 1" bigger but they weigh more too.

well, i already pulled the trigger on part 1 of my plan. axle shafts, 4.88s, ARB, and compressor.

like i said, worse case senario is i build it up bad ass for 35s
next is ARB rear locker.... :christianpray3

I've got my 33's I'd like to go bigger but I'm not in a hurry.

hey matt, hows the house? ready to hit the trails with us yet?