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Discussion Starter · #1 ·
So I see that some of you are running 39s and 40s for tires. I'm thinking of running these myself but have some questions. How big of a lift are you running? What other mods have you done to fit your rubber? Any rubbing? Stock axles or aftermarket? If your running stock, how are they holding up? What kind of wheeling do you usually do?
Thanks for any info you can give me on this.:beer:
 

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100dollar man removed his front drive shaft on the trail to run his 38's :thefinger:


What axle are you running in front?

HAve not heard much of an issue on the rears. I think that size is too large for a d44 personally. I would say 60 to run that size. MAybe a very well built d44...
 

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AZ Bulldog would be someone to ask. He's running 40s with a D30 on the front. I don't no the specifics of his build. He has a very nice looking rig.

He wheels alot and is surprised the axles have lasted over a year. He says the D60s are going in when they give out.

I'm guessing that he's not very hard on the throttle.
 

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I've got D60 axles front and rear and a 4 inch lift with 2" spacers (or 2 1/2" spacers...can't recall which). I'm also putting in longer shocks (Fox). I trimmed the inner fender wells and put Xenon fender flares on (not sure if doing those things helped with keeping it from rubbing or not).

I took the Jeep to Tellico to test it out and didn't have many problems with rubbing, but I was on 37" tires at the time. I haven't done any trail rides with the 40" tires yet.
 

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For 40" tires you need at least 6" of lift, aftermarket high clearance fenders, stubby front bumper, wheels with at most 4.5" of backspace, new CV driveshafts, 5.38 gears, chromoly axles shafts, reinforced Rubicon 44 axles (but D60 axles are preferred).

If you wheel hard, don't expect the D44 to last very long.
 

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To fit 40s...get some flat fenders (or modify [cut] your stock ones) and get a 4" or so lift. You'll probably have to do something with the bumpers if you still have the stock ones.

I wouldn't want to drive a JK with 40s and the stock engine. 37s were miserable enough, even with 5.13 gears.
 

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I am planning on 40's (39.5" Iroks).

I am running a Poly 4.5" lift

I have already removed my fender flares and looks like I have enough clearance just with this. Will probably adjust bump stops if necessary, trim some sheetmetal, or install a 1" body lift.

I will install alloy shafts front and rear and run it till it breaks then upgrade.
 

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Discussion Starter · #12 ·
To fit 40s...get some flat fenders (or modify [cut] your stock ones) and get a 4" or so lift. You'll probably have to do something with the bumpers if you still have the stock ones.

I wouldn't want to drive a JK with 40s and the stock engine. 37s were miserable enough, even with 5.13 gears.
My current setup on the Rubicon is 4" TF lift, Mopar RC bumpers (front stubified, rear clearanced), cut the pinch weld, Xenon flat narrows and BFG MT/KM2 37's. think 39.5 IROKs will fit?
 

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I am planning on 40's (39.5" Iroks).
Those Iroks are pretty heavy at 99 lbs each, your axle shafts may not appreciate that weight when they break free and spin.

I am running a Poly 4.5" lift.
I have the same lift + 3/4" spacers and my 37's get hard into the wheels wells and Xenon fenders at times. I suspect you may have to run longer bump stops with 39.5's or 40's and rely more on droop, which isn't necessarily a bad thing.

My 37" KM2's will likely need replacing some time this year, and I'm in two minds whether to go with 37's again or step up to some 40's, but I'm pretty certain I'll be going with KM2's again.
 

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Those Iroks are pretty heavy at 99 lbs each, your axle shafts may not appreciate that weight when they break free and spin.

I have the same lift + 3/4" spacers and my 37's get hard into the wheels wells and Xenon fenders at times. I suspect you may have to run longer bump stops with 39.5's or 40's and rely more on droop, which isn't necessarily a bad thing.

My 37" KM2's will likely need replacing some time this year, and I'm in two minds whether to go with 37's again or step up to some 40's, but I'm pretty certain I'll be going with KM2's again.
Yeah I already looked into this. The 99lbs are for the Radials... I will be getting the bias ply. The Bias is 84 lbs. Thats only 3 lbs heavier than the 37-12.50 Irok radials I'm running now.

I know I will be on borrowed time, but like I said run it till it breaks then upgrade :)



As far as rubbing goes. I have not had any issues with mine rubbing at all with the poly 4.5 and the 37's and full factory flares :confused:
 
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