bigsikpup

I went with 37's....and I use mine....Thx for helping me out with the decision

SoK66

[QUOTE=Maertz;3787475]Im scared of 37's on my 44./QUOTE]

No reason at all to be. Stock JK Rubi D44s handle 37s just fine provided some common sense is used re: axle reinforcement up front & upgraded shafts in the rear. I've run 37" KM2s, then MTR/Ks for 45k, originally on MT CIIs, then TR HD beadlocks , no issues whatsoever. My rig is no mall crawler, I'm 2 1/2 hours from Moab and over there a lot.

As for the OPs question re: 38s / 40s, whoa. 37 is pretty much the limit before you have to face up to axle upgrades. 38 vs 37 doesn't sound like much, but the weight difference is significant and virtualy all 38s are 14.5" width. Meanwhile 40s take you into a whole 'nother realm of required beef.

MOPWR2U

I just went through the 37 vs 38 vs 40 decision making process this week. I've got a 3" lift on my JK, so with flat fenders I was thinking I could go to 40s pretty easily. Then you start adding up the cost...

For me to trade in my current 35s for 37s it cost me $800.77 for the new tires (got the price quote today), and I don't have to spend a penny on the rest of the Jeep.

For me to change to 40s it cost me $1208 for the tires, but I have to add $360 for the flat fenders, $1600 for 5.13 or 5.38 gears, and another $2200 for Ram Assist. So the 40" tires cost me $5368, vs $800 for the 37s. And that is coming from someone that already has the Dana 60 axles.

I didn't think it was worth the extra $4600 for 40s. I don't like the lack of tire coverage with flat fenders when wheeling in muddy terrain, which is about 3/4 of the year around here. And I don't like the decrease in hillclimbing capability with a short wheelbase Jeep that is not stretched, and sitting at the extra height that comes with 40s. I went with 37s. How boring is that?

JE8154

You're running 37's on a 3" lift with stock fender flares? How much bump stop do you have? Hydro assist isn't something you only need or will want with 40's. It really makes wheeling so much more enjoyable when you can actually steer.

petef550

Do the DIY ram assist for about $500.

MOPWR2U

Yah, I didn't spend a lot of time researching a ram assist. I went to PSC's web page and looked at one of their better systems, and it was $2200. I also guessed a little low on flat fenders for $360. After more research, most of the flat fenders that include inner fender liners, which I would want, at least in front, are about $700. So, to do it right, ... the difference for me becomes:

37s = $800

40s = $5700

And my wife just spent $6000 on new carpet for 1/3 of the house. Guess you know why I went with 37s.

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I would be interested in hearing more real world opinions on how 40" tires can affect hillclimbing ability on a standard wheelbase 2 door JK. If anyone can report on that I'd like to hear it.

MOPWR2U

I thought everyone knew that a Teraflex 3" lift, on a two door JK, really gives you 4 1/2" of lift. That's what I have, a 4 1/2" tall, 3" lift, and the 37s fit fine. Jeep already trimmed the pinch seam on 2013 and newer JKs, so all I had to trim is the plastic inner fender liner at the back part of the rear fenders.

Invest2m4

Lift height has no effect on the amount of bump stop needed. You have to stop uptravel at the same spot regardless of lift height. He was asking about bump stops because you'd need a lot to run 37s with stock fenders. The downside to your setup is you're losing a lot of travel and creating a higher center of gravity.

JE8154

Yea, I ended up looking through the pictures you have on photo bucket. It looks like you're cheating yourself out of a lot of shock up travel running like 4" front bump stops.

Wsullivan1221

Like everyone else has said, if you want 40s you will need new axles, driveshafts and some (optional) not as important things for precaution (I.e steering assist, superchargered, 8 lug bolt pattern). If you have all those things, you should have one hell of a Jeep... But probably no more money