Looking for first hand experience 31's vs 33's

I just re-geared to 4.56, and have been running 31's since I bought the Jeep. My friend got new tires and is offering me his 33x12.5 BFG's for an incredible deal. I am just looking for some input mostly relating to gas mileage.

Has anyone gone from 31's to 33's with 4.56's and noticed a big decrease or increase in gas mileage? I am mostly concerned with highway mileage, theoretically it should be better with the 33's right??

mileage doesnt get better with bigger tires... any theoretical gains are lost once you factor in the extra weight of all those tires, the aerodynamical loss from 1.5" of lift, the wide 12.5 footprint...

i dd a rig on 4.56, on 33x12.5 muds, and a coworker runs 33x12.5 A/T's on 4.56.
mileage sucks, if you have to think about it too much, stick with 31's. but 33's give you a much better stance imho, its worth any negatives.
being awesome aint easy, get a 2nd job if need be, you need 33's.:05of5:

xcm said:

mileage doesnt get better with bigger tires... any theoretical gains are lost once you factor in the extra weight of all those tires, the aerodynamical loss from 1.5" of lift, the wide 12.5 footprint...

i dd a rig on 4.56, on 33x12.5 muds, and a coworker runs 33x12.5 A/T's on 4.56.
mileage sucks, if you have to think about it too much, stick with 31's. but 33's give you a much better stance imho, its worth any negatives.
being awesome aint easy, get a 2nd job if need be, you need 33's.:05of5:

Click to expand...

4.56 and 31" is seriously overgeared. I have a hard time believing he wouldn't get better mpg with the 33" tires. The weight only matters when you're accelerating. The footprint is not that big a difference.

I had 4.88s and 32s for a year of mostly DD and wheeling. Torque was awesome, mile-age sucked at about 12-14mpg with a heavy foot city (pretty much at least one burn out per tank). Now I'm on 35's with my 4.88 gears...haven't had a full tank yet, but I will in a week.

With that I say 33s. We didn't buy Jeeps for the mile-age, and worst case...remember, you're still getting better mpgs than grands with a v8 lifted with tires.

~Scott

winkosmosis said:

4.56 and 31" is seriously overgeared. I have a hard time believing he wouldn't get better mpg with the 33" tires. The weight only matters when you're accelerating. The footprint is not that big a difference.

Click to expand...

what tire size do you run?

Thanks for the input. I am already lifted enough(around 4.5") for 33's, so all I'd need to do is trim and mount 'em up. I am mainly asking about highway mileage because this is not my daily driver, and when I go camping/wheeling it is usually a 400 mile road trip to get there. Right now, I can cruise at 60-65ish(speedo is way off, so I'm going by the speed of traffic) at just UNDER 3K rpms. Too me, that seems high and way over geared. I'd like to be able to cruise around 70-75 and not suck my gas away.

Around town, it's awesome right now. Torque is unlimited, and with just driving streets with speeds up to 55 I'm half way through a tank and my odometer thinks I've gone 215 miles..... of course that is off though, thanks to the gears. Haha.

And hey, who can pass up 4 BFG At's 33x12.5r15 with maybe 40% tread left for $50???? :clap:

winkosmosis said:

4.56 and 31" is seriously overgeared. I have a hard time believing he wouldn't get better mpg with the 33" tires. The weight only matters when you're accelerating. The footprint is not that big a difference.

Click to expand...

thats not true. at highway speeds 50% of the work the motor is doing is to simply overcome wind resistance and maintain speed. more rotating mass would only hurt this number. but at if the OP is running 3k RPMs at highway speed, i think 33s wouldnt be undesirable.

do you have an automatic or manuel transmission? will your buddy let you roll around town with them for a day or two? my buddies would... on a side note, the best way to test calculate your milage and speed since your speedo is off is to go on a long drive and take notes according to a GPS.

VAhasnoWAVES said:

thats not true. at highway speeds 50% of the work the motor is doing is to simply overcome wind resistance and maintain speed. more rotating mass would only hurt this number. but at if the OP is running 3k RPMs at highway speed, i think 33s wouldnt be undesirable.

do you have an automatic or manuel transmission? will your buddy let you roll around town with them for a day or two? my buddies would... on a side note, the best way to test calculate your milage and speed since your speedo is off is to go on a long drive and take notes according to a GPS.

Click to expand...

At constant highway speed the rotating mass doesn't matter at all. It only matters when you're accelerating that rotation. The only things to worry about on the highway are air resistance, tire rolling resistance, and drivetrain friction.

33's and 4:56 shouldn't be a problem

< 33's and 4:10, but ran 3.07/33's for a long time, maybe I am just easy to please

VAhasnoWAVES said:

thats not true. at highway speeds 50% of the work the motor is doing is to simply overcome wind resistance and maintain speed. more rotating mass would only hurt this number. but at if the OP is running 3k RPMs at highway speed, i think 33s wouldnt be undesirable.

do you have an automatic or manuel transmission? will your buddy let you roll around town with them for a day or two? my buddies would... on a side note, the best way to test calculate your milage and speed since your speedo is off is to go on a long drive and take notes according to a GPS.

Click to expand...

I have an automatic. Turns out 2 of the tires are worse than he thought, not really worth keeping. So I have 2 33's in my backyard now, if I find 2 more for a good deal I'll run the set, otherwise I'll save up and get my 33x10.5 KM2's that I want.

i think thats the ticket. or save and buy a good set of 33x12.50s. you have 2 full size spares.

winkosmosis: lol, XXXXing lol. your too funny.

nitrogt101 said:

...otherwise I'll save up and get my 33x10.5 KM2's that I want.

Click to expand...

I'd wait and see what uber xj thinks about them after he gets his siped. I walked all over the place at Evan's yesterday on open diffs and his KM2's and locker gave him a worse time than my MTR Kevlars.

Torx can vouch for the KM2's with the center lugs siped, big difference. I'd save for siping if you're set on the KM's.