30s vs. 31s?

Okay I understand that 30s and 31s probably is not much of a difference but...does 30s look alot smaller than 31s? Reason I ask-will having 30s have much better gas milege than the 31s? Any input?

Depends on the brand of tire, IMO. Most 30's are 9.5" wide, most 31's are 10.5" wide, which also helps them 'look' bigger.

neither will be great with stock gearing

all depends on tires. Some tires run small, like BFG's. 31's actually measure 30.8. So if you comepare bfgs at a 30" and 31" yes there will be an inch difference but like i said depending on tire. If you are worried about gas mileage, i would say the difference is minimal. Im now at 32's and actualy see better gas mileage...how you ask???... I changed my fuel filter, and it was horrible looking and changed plugs. much better now.

You will be increasing rotating weight considerably over stock tires. This is bad for fuel economy, acceleration and braking... blah blah blah
Bottom line: 31s will get worse gas milage than 30s. Alloy wheels will help. You will need to re-gear if you want either size to perform decently on or off road. I run 30s on stock gears and with a heavy foot over 500 miles highway and city still manage 18.5 MPG. Most with 31s report 17ish, that I've read.
Acceleration and hill-pulling will both suffer greatly on 30 or 31s unless you re-gear.

Both my 98(rip), and my 97 saw an increase in mpg when I went from the 225's up to the 31's. The 98 got as high as 22 with the 31's. 97 tops out around 20.

I suspect any increase in MPG would find its roots in highway driving at the same speed, keeping the motor at lower RPM. Flat ground, too.

i have a 96 with a 3" lift and 31's and my brother has a newer wrangler with a budget boost and 30's. his look puny until you put them next to each other and you can see that they are almost the same size. i tihnk his are 9.5 wide and mine are 10.5. also mine are m/t's and his are slightly worn street tires. his look pretty retarded in my opinion so i would say go with 31's. and like someone mentioned you will probably want to consider regearing. its not necessary but you will appreciate it afterwards.

Wranglers have rather large wheel wells, they NEED bigger tires to not look dumb. People will say if you go 31's it will be a dog on the highway. I have 31 M/T's on mine and they give me no problems on the highway. I drive 37 miles on way to work six days a week and deal with hills and many a few on ramps/mergers. My AW4 does not get worked very hard at all, I cruise right up the hills without issue- not major hills, but hills that are 1/2 mile long at constant grade, I don't even downshift. The gas mileage difference between the 235's and 31's is minimal at best. Look at it this way...you can get an extra 15 miles out of a 20 gallon tank if you're lucky, or have tires that don't suck.:rof:

As it has been already said, the milage question is much more affected by driving style than by the 1 inch difference. And of course, the standard line is every jeep is different. I have 31" MTs and get a consistant 14 mpg. Sounds bad, but I have 5" of lift and drive 80mph up hills. If you are that worried about the look, I have noticed that an aggressive tread like MTs tend to look like a bigger tire than an AT tire. Good luck, but be very wary about taking mpg information from this list. Everyone has great intentions but many people fail to include the little details that justify why they are getting what. Not to mention many people don't really know how to figure mpg and guess based on how many miles they get out of a tank, (don't laugh, its pretty common). Good luck with whatever you decide.

when I went to 31's and stock gearing i really didn't notice any difference. You certainly don't need to regear with 31's. 32's and above is when the stock gearing starts to dog down. 31's will look better and perform better (bigger tires, smaller rocks).

mucovich said:

when I went to 31's and stock gearing i really didn't notice any difference. You certainly don't need to regear with 31's. 32's and above is when the stock gearing starts to dog down. 31's will look better and perform better (bigger tires, smaller rocks).

Click to expand...

I tend to agree you don't HAVEto regear going from stock tires to 30" or 31" meats, but it sure helps. I went to 31s from 235x75 stock tires but was annoyed with the engine lugging especially in O/D (have the AW4). I regeared from 3.55 to 4.11, and actually improved my highway mileage, because the engine was turning at a higher RPM at 65 MPH (2000 to 2300 RPM), and was more efficient at this RPM. Also, if you change to larger tires, regear, or both, be sure to change the speedo gear to accurately reflect your speed, or you just may think your mileage sucks.