Several questions on running 37s - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 10 Old 01-06-2012, 11:26 AM Thread Starter
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Several questions on running 37s

I have a 2012 JKUR with PSC crusher flares, RR XHD modular stubby, OR-Fab rear tire carrier(pending), RRoR full skid system(pending) and the PSC Evap skid. I plan to DD the Jeep, wheel 6 or more times a year and take as many road trips as possible. Just got back from some OHV trails in Chippewa national forest.

I am considering running 37s on a 2.5" RK stock mod lift plus a 1" BL, appropriate bump stops and a re-gear. Not sure about the 1" BL as I am still sorting through a variety of threads and builds. I read through the primary how-to thread for 37s on 2.5, https://www.jkowners.com/forum/showthread.php?t=31183

Questions:
I have not found, or overlooked, a specific note or thread on the necessity of having a better lift for 37s that includes upper and lower control arms. Are these other components of a more complete suspension lift necessary for 37s over 35s?

I've heard that the bigger tires add stress to the transmission. Would that not be alleviated by the appropriate re-gear? For example, gearing to go back to stock RPMs at a given speed and adding overhead gearing to account for additional rotational mass. I would be less concerned about top speed and MPG compared to stress on components.

What might be the priority list of component upgrades/reinforcement for 37s?

Should I consider what I found in the thread linked above as "gospel"?
- "Install front axle sleeves, C gussets, box in lower control arm brackets with skids, and reinforce trackbar bracket on front axle:"
- "Install chromoly front and rear axle shafts"

I will not be beating on this Jeep, I hope, and have no issues backing down from an obstacle. I would go with 35s but I get the impression from other owners that I might regret not starting with 37s. But, it could be I'm just not ready for 37s as a new Jeeper.

Thanks
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post #2 of 10 Old 01-06-2012, 11:30 AM
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i DD my JKU sport and i have a 3.5" RE standard kit, 37's and 5.13's and that is it and it is perfect! I will be tossing the RE kit for a long arm and i have heard that the drive on road with a long arm is a lot better so i would do that! 3.5" long arm kit... either RK or teraflex! and you will be set! is it auto or manual??? also do you have pics of it now?

-Marc
2010 JKU -- 3.5" RE Lift -- EVO LCAs -- ARTEC Truss and TB mount -- 17" Procomp 7069 -- 37" Maxxis Treps -- Heated Trucklite Headlights -- Synergy Drag flip -- Synergy TR -- Synergy bj's-- EVO 1/4 Pounder -- EVO Tire Carrier -- 4 gal rotopax -- TF Third Row -- China AEV Snorkel

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post #3 of 10 Old 01-06-2012, 11:53 AM Thread Starter
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It is an automatic. I bought Goodyear Wrangler SilentArmor tires for winter and this road trip. It would be ideal to find a 37" tire that will work on our sometimes icy roads in IL and off-road.
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post #4 of 10 Old 01-06-2012, 11:55 AM
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You have a Rubicon so I don't think sleeving and chromoly shafts would be a pressing issue. You may want to put some inner C's though, they are cheap. A regear will keep your ride way more tolerable with the 37's. I haven't heard of added stress on components. I would probably go with the 3.5" long arm though and ditch the 1" BL since your a 4 door, I would be more concerned with COG on a 2 door. Planman's builds are epic but that one in paritcular is for COG minded and specific to his 2 door. 4 door is a little more forgiving

-Dan

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post #5 of 10 Old 01-06-2012, 11:57 AM
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Quote:
Originally Posted by CF1973 View Post
It is an automatic. I bought Goodyear Wrangler SilentArmor tires for winter and this road trip. It would be ideal to find a 37" tire that will work on our sometimes icy roads in IL and off-road.
I donít know if the GY Duratrac comes in a 37. You could get the Falken Wildpeak in 37 though and it probably performs good in snow and ice. It isnít as aggressive as a MT or Duratrac.

-Dan

2008 JK X: Sold
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post #6 of 10 Old 01-06-2012, 12:03 PM
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Check out the RK's new system, the 2.5 inch flex. Just came out in the last couple weeks I think. It is basically a go between the 2.5 inch stock mod and the 2.5 inch max travel. It adds front lower control arms and front extended brake lines for caster adjustment. I dont think that you would even need a body lift honestly, I may be wrong but...... Just make sure you address bumstopage before offroading. Good luck!

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post #7 of 10 Old 01-06-2012, 12:09 PM
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**I edited this**

You *can* run 37s on a 2.5 Stock Mod, but I think you'd be happier in the end getting your belly up and over rocks and such if you get into more serious wheeling. The JKU is a long beast and that extra inch will help in the end. If you had a two door I'd just tell you to buy the Max Travel and give it hell (that's what I did). If you go the 2.5 route on yours look at the 2.5 Flex System - the lower control arms up front will be nice for keeping it driving like stock.

The Rock Krawler systems are upgradeable of course, so you could start with the stock mod and change it up from there, but just remember you're going to need to replace sway bar discos, coils, add the arms, ect if you buy the stock mod to start. You will only end up re-using the front track bar and rear track bar bracket if you stuck with RK. Therefore, I would consider turning your attention to a 3.5" lift and ditch the body lift.

Long arms are a marginal improvement in overall capability on the JK and a much more involved installation process. The ride will not really be too effected by mid vs long arms until you get up over 4.5 inches of lift or so.

In regard to going with all 8 arms over just the lowers - I would go with all 8 arms and 3.5 inches so you can really dial the thing in to drive as stock like as possible after it's lifted.

With a 12 you'll need to address the exhaust with either Tera-Flex exhaust spacers or the AFE Y-Pipe. Both are proven to fix the issue with the drive shaft hitting the exhaust.

Many guys are saying that the 12s are bearable with 4.10s and 37s with the new motor and transmission. Re-gearing will help, but the jury is kind of out on the 2012s at this point.

The Falken Wildpeak is a great option for an overland type tire that can be pushed very hard in the rocks. There is some very impressive documentation on that tire kicking ass in the rocks, mud, sand, ect.

Welcome to the forum!

Marcus


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post #8 of 10 Old 01-06-2012, 12:55 PM
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Here is our Jeep on 37s and on a 2.5 RK lift.

Road///Race Motorsports (562)906-0080 10am-5pm PST Toll Free Order Line 855-891-1898

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post #9 of 10 Old 01-06-2012, 01:05 PM
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/\ niiiiice!

-Marc
2010 JKU -- 3.5" RE Lift -- EVO LCAs -- ARTEC Truss and TB mount -- 17" Procomp 7069 -- 37" Maxxis Treps -- Heated Trucklite Headlights -- Synergy Drag flip -- Synergy TR -- Synergy bj's-- EVO 1/4 Pounder -- EVO Tire Carrier -- 4 gal rotopax -- TF Third Row -- China AEV Snorkel

Coming up:
D60 Front 99-04 Ford ARB w/ 5.38
14 Bolt rear ARB w/ 5.38
EVO Long Arm
40/42Ē MTR's
17" Spyderlock Beadlocks
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post #10 of 10 Old 01-06-2012, 06:06 PM
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I like the 2.5 myself. I have the 3.5 , nuthin wrong with the 3.5 but ive driven a 2012 with 37s an the 2.5, the onroad manners are alot more solid. Plus im a fan of LCG. If your gonna run 37s do the gusset an sleeve kit. Its just cheap insurance. Also 4.56s would be perfect for the 2012 with 37s
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