New tires with stock gears?

So I have 2 questions...(tried searching...failed).

1) If I get 31" tires, will my XJ become "gutless"? I have an '89 limited...I have no idea what the gears are but I have Dana 35's front and rear if that means anything. I just want to make sure I wont have to make a gear switch with 31"s.

2) Is it OK to run 31" tires on the stock 15x7 rims for a few months? I know they recommend 15x8 at a minimum...but I dont have money for new wheels.

Thanks.

do it, no big loss. even on stock wheels.

I put 31's on mine, 97 with a 2" budget boost. It definitely has less oomph off the line, but I'm not drag racing. Most of my driving is highway, off road stuff is sugar sand or sloppy mud. No big deal.

Stock rims too,

Mark

i had 31's on my 88 and it really didn't have any power to begin with(renix) so i really didn't notice or care about the little bit of power loss. and the stock rims are fine, i've even seen people run an 11.5inch tire on stock rims.

a D35 up front???? are you sure about that????

im willing to bet that you have a Dana 30 up front.

there will be some loss of power with 31" tires and stock gears. i did stock gears turning 32s and 31s for a couple years before i regeared. it can be a PITA if there are a lot of hills, freeway driving, or overpasses where you drive. the tranny will have to downshift and raise engine RPMs in order to accelerate from normal highway speeds (like passing or going up hill).

i had my 32" MTRs mounted on stock rims for a while. the backspace caused a bit the tire to rub the lower control arms at full lock. the sidewalls also looked like they ballooned out a little, but nothing major. i didnt loose a bead with those rims.

correction...dana 30 up front.

Alright guys, thanks...that the reassurance I wanted.

Anyone have experience with trying to get costco to mount 31"s on 15x7 rims? I plan to just bring the wheels in to get them mounted and centered, since I know they're going to turn me down if I drive my Jeep in (To big of size...they say...).

yeah, good call..... cause the boso's at a lot of tire shops don't wheel....

There is a 2 mpg loss when I go from 30 inch tires to 31 inch tires. Also, I run my XJ in 3rd gear instead of drive unless I am on the freeway doing 60 or more, in order to only lose the 2 mpg. When I go to 32s it is a complete disaster. I run 8 inch rims, but 7s are fine.

are you calculating for the amount that yuor speedometer, and odometer are off when you check for mileage? that's probably your 2, or close to it...

DeathValleyPaul said:

There is a 2 mpg loss when I go from 30 inch tires to 31 inch tires. Also, I run my XJ in 3rd gear instead of drive unless I am on the freeway doing 60 or more, in order to only lose the 2 mpg. When I go to 32s it is a complete disaster. I run 8 inch rims, but 7s are fine.

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Thats funny, i gained 2mpgs when driving highway speeds with cruise control doing the speed limit. Cause with a bigger tire your turning less rpms, but yes you have more rolling resistance. But stock gears which are probably 3.55s are fine with 31s. I'm running 35s on my Cj with 3.73s and it does fine.

But I have 2" lift with the stock alloys and they do fine. I get some rubbing at full lock, but I just steer back a hair and it goes away.

31s are perfectly fine with stock gearing. I can barely tell the difference compaired to 29s.

31x10.5's BFG muds on factory 15x7's RC 6.5" with 5spd and 3:07's. I notice a bit less oomph but it was no race car before w/235's.