Hey, so a few months ago I bought some 31" Goodyear Duratrac tires and have been burning the tires I have on my XJ out. Its about time to put them on, but now Im thinking about moving up to 33" Duratrac tires. My question is does anyone know how much drop in mpg there is when moving up from 31" tires to 33" tires and would my stock Dana 30 and Dana 35 with stock gearing be able to handle them? This is a daily driver and I go on the highway alot. Thanks for your input!

 

It will be a little sluggish with 33's and stock gearing unless you have a manual trans and you wont notice it as much. The dana 35 is junk but will do ok as a dd with 33's as long as you dont get on it to hard too often. As far as mpg difference, not much. You will lose 4 or so mpg just with the 31's and maybe one more with the 33's. Depends on tranny and driving style.

 

I wouldn't ever go more than a 33 on a D35 though. x2 on everything else above.

 

Would definitely not run 33s with a dana 35. Its just that the axle wasnt meant to support that heavy of a tire. Personally i wouldn't do it. Your mpg will definitely suffer. Keep in mind stock 3.55 gears are not gonna handle 33s that well. Its up to you man its your jeep. Just know that those big ol tires will put a strain on both your axles and engine. Just my 2 cents

 

Thanks for your input! I was leaning more towards not doing it, but I wanted to just see what others had to say. I always thought that 33's would be too big, but someone was telling me otherwise. Again thanks! I'm going to just stay with the 31" tires I have waiting for me and call that good.

 

my mpg went to crap when I went from 30's to 31's lol

 

Your initial jump to 31's is more of a difference than increasing to 33's would be. If you'd like 33's, go for it. If you don't like 'em, you can always find someone who's willing to trade 31's for 33's, everyone wants bigger!

That being said, bigger anything is more stress than the part in question was originally designed for. There are folks out there who could tear up a Dana 35 with stock tires on it, and there are Dana 35's running around with 38's on them. Your the driver, you (for the most part) decide how hard you beat on it.

The mysterious grenading Dana 35 myth is just that. People break all kinds of stuff while others don't. Bolting a 33" tire on a Dana 35 won't break it.

 

I had 31s and was getting 16-17mpg

Now 33s and I'm getting like 12-13mph

 

31s are not a bad tire size. They're usually common and will cost less money. Some people prefer the BIGGEST BADDEST look for their jeep. And thats cool, personally i prefer the most comfortable economic setup. Remember jeeps are like shoes, Are you shopping by looks or fit and function?. Its up to you to answer that question.

 

Plus if these 31s are new, run em. If you try and sell em, you'll lose some money.

 

so ive got an 89 xj limited...3 inch lift on 31s...200k miles...what the hell is causing me to get like 6mpg? i dont drive it hard...just doing 55-65 mph for about 30 miles and back home i burned up half a tank....
any ideas or suggestions on how or what to fix/change?
i love the hell outta my xj...and if i cant get the mpg fixed...ima have to trade it for something gas saving....eewww honda....

 

all your sensors in working condition? o2s are able to do that as well as vacuum problems. vacuum would make it run crappy. i suppose it also depends on your gearing. but 6mpg sounds like you're running rich also you cant go off odometer readings since you went 31s because its wrong.

 

as far as i know it runs just fine...but i put 20 in earlier...went a total of 62 miles and while pulling into my drive way my low fuel light came on....my vaccuum works fine i think....cruise control and air blower selector works....could it have something to do with the lack of a vacuum line coming from the valve cover to the air box?

 

Thank you guys for all the input! After hearing what the mpg was between the 31's, and the drop for 33's I think I will just put on the 31's and call that good. Also after thinking about the trails I take and what function they would serve, I believe I was getting caught up in the Biggest Baddest instead of what will serve a purpose. Ill be putting those Duratracs on this weekend!

As far as your issue overkillstinger I have heard that if the o2 sensor goes south, it can cause a drop in gas mileage.

 

finally someone said it. bigger tire + stock speedo gear = incorrect mileage calculation.