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Going from 30" to 31" what needed?

Jeff-97XJ

NAXJA Forum User
Location
Atlanta, GA
97XJ, 4.0, 231J, 3" Old Man Emu Lift.
OME JC1A Rear Leafs
OME 930 A&B Front Coils
OME 36C Rear Shocks
OME 35C Front Shocks
Original control arms.

Currently running 30" Goodrich AT's.
Need to replace tires and would like to know what would happen if I buy 31" new tires?
Do I need new control arms?
Do I need more lift?
DO I need fender trimming?
If it isn't too complicated or expensive, I would really like to put on 31's.

Any advice is appreciated.
 
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Currently running 30" Goodrich AT's. Need to replace and would like to know what would happen if I buy 31" new tires?

What would happen ? You will have new tires and the Cherokee will be 1/2 inch taller. 31's fit with a 3 inch lift. With stock rims they might rub the control arms or the front bumper plastic.
 
Assuming stock wheels, 31"s will rub on the lower control arms, adjust the steering limits to eliminate or replace with aftermarket LCAs.

The front fenders will need some trimming as well as the front bumper. It's all plastic so it isn't very difficult.
I use an 4-1/2" angle grinder, with a 120-grit flapper wheel, to shape and trim the plastic. Outline the desired shape with masking tape to guide the trim.
The tires may hit the rear pinch seam, in the rear of the front wheel well, hammer it flat, if necessary.
There may be minor problems in the rear fender too that will need trimming.

I was fine with 30"s but when changing to 31"s a decade ago, it was enough of a change to convince me to regear to 4.11s.
We spend a lot of time in the mountains, where the lack of gearing was noticeable, along with the reduced braking power.
Having a mostly stock 97 and a built 2001, it's easy to remember what stock feels likes.
 
Why are posting the same question in both the OEM and Modified sections?
Since this a "Modified" question, it shouldn't be in the OEM forum at all.
If a moderator see this, this thread should be combined with the posting in the Modified forum.
 
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My experience is you DO NOT need fender trimming to run 31s. You may rub in extreme situations, but not regularly. Even with 32s and trimming I still run sometimes. With aftermarket LCAs I rubbed with stock 16" rims. I remedied it with a couple washers in the "stop nut" in the knuckle.

I say get the 31s and run them. If you find an issue, fix it. You'll hear dozens of reports of what you "need" from an SYE, to a t-case drop, to a half dozen other things. The rule of thumb with XJs is that everyone has different "needs."
 
I say get the 31s and run them. If you find an issue, fix it. You'll hear dozens of reports of what you "need" from an SYE, to a t-case drop, to a half dozen other things. The rule of thumb with XJs is that everyone has different "needs."

I agree most with this.
If you want 31's, then buy the 31's.
It will be drivable with your current setup, just may take some small adjustments here and there.
 
You can eliminate any possibility of rubbing by adjusting the bump stops...if you don't mind losing suspension up travel
I always have set the suspension to maximize the travel, both up and down.
To get as much up as possible, my 2001 needed trimming. YMMV
 
I'm with lazyxj 100% - I put on a set of 245/75-17 (which are 31.5" true) from my normal 30/9.5-15 (29.75" true) and my 2000 Jeep was a DOG with the stock 3.55 gears. Gas mileage dropped from 16 to 12 and it would struggle up some of the hills in the upstate of SC. It seems that the 30 to 31 tire size is the breaking point for stock gears. I have since gone back to the 30s and kept the 31s until I can regear to 4.11 also. Braking power was also diminished. Enough that the lady did not feel comfortable driving it until I did a ZJ disc swap and put the 30s back on.

On my Jeep, even the 30x9.5 would scrub the control arm on the left side, but would not make contract with the flare thanks to the bumpstops. I did trim some, but 75% of my stock flare is still there. Of course if you have the older body style, the wheel wells are larger and rubbing is decreased also. This is all based on the stock wheel backspacing. The 17s I have are 4.5" backspacing and do not have any scrubbing issues.
 
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