Need your thoughts on this. My brother and I were talking the other day about the crappy MPG my truck gets (for the record, about 16 MPG driving nice and easy, and low RPM shifts), and we were discussing the possibility that MPG may actually INCREASE by running larger tires such as 33's. The theory being that since Xterra's are geared so low, yet have ample power for their size, so switching to a larger tire would enable you to roll along at a lower RPM to maintain the same speed. The question is: Would the extra weight and rolling resistance of a larger tire negate any potential gains you may achieve with running at the lower RPM???

I am very curious about this; anyone who switched to a larger tire, let me know what your MPG difference was before and after. The only experience I have with this is in my last truck, a 94 4Runner. It was only a 4 cyl, so it got half decent mileage anyways with 31's, but when I switched to 33's my mileage dropped substantially because the 4 banger had to work double time to turn the big tires (ie. 5th gear on the highway was a pipe dream unless you were going downhill in a tailwind.)

The extra resistance involved with turning the larger rubber probably makes it a wash...but, that said, my 33's dropped my cruising rpm way down...so, I did get a ~ 20% deeper over drive in the deal.



BTW - When you went to the larger tires...you were drivig faster than the speedo said, and going further than the odometer said...

So - your speedometer says you're going 60, and the odometer says you went 200 miles, it took 10 gallons, so you figured you were getting 20 mpg, averaging 60 mph...

Then, you swap on 33's, so you're going 70 when the speedo says 60 mph....and, the odometer says you went 160 miles, and it takes 10 gallons, so you figure you dropped to 16 mpg averaging 60 mph....but you are still getting 20 mpg going 70 mph.

Yeah, that's what I was thinking. You swap on the larger tires, so you are actually going further and faster than what your speedo/odo says, but even when you account for this difference, do you think that running 33's will give you BETTER gas mileage in the X overall, or worse. I am of course assuming that when you swap to the 33's, you keep your ACTUAL speed at 70mph, even though your speedo indicates you are doing 60.

anybody else??? Looking for feedback.

I think if you were at 55mph for the whole gas tank, yea you'd see an increase - but the problem lies in the start and stop traffic. It takes more gas/power to turn the larger tires for acceleration and I think this would negate if not make worse your gas mileage

With that said, I get the best gas milage in my camaro with it right in it's power band on the interstate cruising at about 3grand. Anything lower and I find myself stepping on the gas pedal a little more to get the same results for going up hills/etc and it generally results in lower gas milage. I think with larger tires you may end up lowering your cruising RPM enough to make the same sort of difference, IMO.

Yes. My mileage went up w/ 33x12.5 BFG M/T's. The extra weight/drag was never an issue. I went from consistently getting 15 mpg w/ 31x10.5 BFG A/T's, to 18 mpg consistently w/ the 33" M/T's.

Of course, once I added more steel and a winch, I'm now back to 14.5 mpg...