Are 31's worth it?

[xjstock++]

My DD is a stock 2001 XJ (4.0 auto). I'm planning on building it to be more capable for Colorado/Utah trails while staying close to stock...and my small budget

I'm going to install a RE 3.5" lift in the next few months and I'm trying to decide if it's worth getting bigger tires ASAP (31x10.5s), especially considering that I'm currently running practically new 235 75 r15 AT's & I'd probably need to re-gear to make the 31s perform. Are 2" bigger tires going to offer enough advantage to justify ditching my 235s, buying new wheels, and re-gearing? Should I compromise & get the 31s but stick with stock wheels and gears?

 

[whitexj98]

Get the 31s, if you hate the power loss/ gas milage, then regear. Sell your tires while thier new and 31x 10.50s will work fine with stock wheels.

 

[01greenxjsport]

get the 31's and save the 235's for spares or for street drivin if u get aggressive 31s

 

[FlexdXJ]

31's are a bit wider, have an inch more ground clearance and aren't really that bad on stock gears. I have 31's on a BB and other than it needing a little bumpstopping and trimming in the rear its fine.

 

[old_man]

I have run almost every trail in Colorado in the past on 31's. It takes a bit more finess and thought but I think I actually enjoyed the challenge more than now with 35's.

 

[xjstock++]

Thanks for the advice... I thought I'd probably want the 31s. My main concern is trail performance - will 31s w/ stock gears be a net performance gain on the trail?

 

[old_man]

A lot depends on your gearing. 31's will give you better ground clearance and most likely a boost in traction. If you are geared too high, your performance may suffer. What is your ratio?

 

[whitexj98]

Yes it will be a gain, in 4 low you won't notice any loss.

 

[xjstock++]

Thanks again for all the replies.

I've got the 4.0 auto, so I'm guessing my ratio is 3.55. I know 4.10 is ideal for 31s, but I'd like to put re-gearing off until I can save up for an ARB or eLocker (I want to keep open diffs for ice).

 

[thechief86]

i say get 32's or 33's for that much lift. it isn't that bad with 3.55's at least till you can afford to regear. if you don't think you'd be able to regear within the life of a set of tires, then i'd go 31's or smaller. i personally wouldn't regear for 31's if you plan on going bigger later. it sucks to have to regear more than once. just from personal experience.

 

[NW-ZJ-SCOTT]

31s and 3.55s is just fine.. Its really not that bad of a change..

I suggest sticking to 31s and 3.55s untill you are at a point of going bigger. I have been doing 33s and 3.55s for awhile, the loss of power has been substantial, and i am ready for 35s or 36"s.. so NOW is the time to gear for me

 

[Darky]

I ran up in Big Bear out here with 33s and tock 3.55s. Keep it in 4low off-road and you'll be fine. With 31s, you'll probably be fine in 4 high even.

 

[xjstock++]

So most performance loss with 3.55s & 31s will be felt on the highway and gas pump, not the trail?

 

[Darky]

I didn't notice anything other than not being able to outrun Civics anymore when I stepped to 30s from 235s. I got a best tank of 22 mpg with the 235s, averaged 19-20ish I think. I averaged 18-20 on 30s.

 

[wy_jeep]

You could also go with Moab wheels and 245/75/16 tires (off of a Rubicon). The tires are just under 31" and a little narrower than 10.5". I swapped those onto my 98 XJ (3.55 & auto) about a year and a half ago. It drives just fine, honestly I didn't notice the power loss.

 

[the_weirdo]

So most performance loss with 3.55s & 31s will be felt on the highway and gas pump, not the trail?

If you live in a "hilly" area you will feel it a lot more than guys in flatlands - you will barely be able to get into OD with an auto tranny. I hated 31's with 3.55s and had to regear within a week. It depends on how much power loss you can tolerate. I would plan on regearing.

 

[Johnnie Walker]

I would say that you should stick with the 235's for now. Especially since you just got them. I have 235s now and am going for about 3" lift, I do not plan to go any larger until I need new tires, and no larger than 30s if I do not regear. I feel as if my XJ doesn't have a lot of guts as is.

 

[drifto77]

If you live in a "hilly" area you will feel it a lot more than guys in flatlands - you will barely be able to get into OD with an auto tranny.

I've been all over the San Juans of S.W. Colorado with my XJ on 31's w/3.55's.
(1st trip I took up there was on 30's)
Even at the top of Imogene Pass (13,114 feet) I noticed NO power loss. Even in 4-hi.
In 2-wd on hi-way 550 I also noticed NO power loss all the way from Durango to Montrose.
It even shifted to OD just like it always does.
The ONLY loss I did notice was the stopping power due to the greater rolling mass of the tires.
But you get use to that.

I say go with the 31's and dont look back.
Just dont try it without lifting the Jeep AT LEAST 2 inches.
Before I did a BB on my '99 I tried my 1st set of 31's just to see if it would work.
NOPE. It rubbed all the flairs trying to get out of the driveway. LOL!!!

BTW....
running 31x10.50's on stock wheels... you will rub your lower control arms at full lock when you turn.

 

[BenDiesel]

if you want gutless try driving a 2.5 wit 3.73 on 3 in lift with 31 on the freeway

 

[NW-ZJ-SCOTT]

if you want gutless try driving a 2.5 wit 3.73 on 3 in lift with 31 on the freeway

I sold some spider gears to a guy that was rolling 3.07's and 35"s..

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