Tire choice quandary?????????

[Explorer 1]

OK, I've probably modified my Jeep Cherokee beyond what would be done for most expedition vehicles, still I seek a little better fuel mileage on paved roads and a ride with a bit less tire noise for those less challanging adventure type treks.

All my research has shown that by lowering the unsprung weight (tire and rim), I can not only increase my fuel economy but also the acceleration. My current tire and wheel choice is on the rather heavier side, 35/12.50/15 BFG KM2's mounted on Raceline bead lockers.

I'm looking for a set of lighter "all terrain" types which I can mount on a light weight rim. Perhaps I can decrease my wheel/tire weight by as much as 30 - 40%.

My problem is that the gearing and suspension on my XJ is set up for a 35" tire. I'm willing to buy larger rims to accommodate a lighter tire but am having a hard time finding a lighter "all terrain" tire with less width and a 35" diameter.

Perhaps someone out there in "expedition land" can help me.

Thanks,
Fred
Explorer 1

[CA-RJ]

According to Tire Rack, the BFG MT KM2 is 61 lbs. The BFG AT is 54 lbs. Doing that and going to a non-beadlocked alloy would certainly shed some weight. If you could find a forged wheel, that would even be lighter. What are you getting for fuel mileage now? What are you hoping to achieve?

[reece146]

I dropped from ~85 lbs per corner to ~55 lbs per corner. Made zero difference to mpg or acceleration.

I'm running GY Duratracs currently. Fab tire over the 1000kms or so that I've had them to date. Grippy, quiet, good winter traction - have yet to try them off-road as wheeling season is currently closed here (sleds rule the trails atm).

GY doesn't make a floatation 35" tire AFAIK, you'll have to switch to a metric 16 or 17 inch wheel to get the same diameter.

[Explorer 1]

According to Tire Rack, the BFG MT KM2 is 61 lbs. The BFG AT is 54 lbs. Doing that and going to a non-beadlocked alloy would certainly shed some weight. If you could find a forged wheel, that would even be lighter. What are you getting for fuel mileage now? What are you hoping to achieve?

Off road more difficult trails mileage can get down to 7-8 mpg, around town 10-12 mpg and best highway, maybe 14-15mpg.

On the highway if I could get into the higher teens, keeping my speed down to 65 mph, I would be most happy.

Thanks,
Fred
Explorer 1

[Explorer 1]

I dropped from ~85 lbs per corner to ~55 lbs per corner. Made zero difference to mpg or acceleration.

I'm running GY Duratracs currently. Fab tire over the 1000kms or so that I've had them to date. Grippy, quiet, good winter traction - have yet to try them off-road as wheeling season is currently closed here (sleds rule the trails atm).

GY doesn't make a floatation 35" tire AFAIK, you'll have to switch to a metric 16 or 17 inch wheel to get the same diameter.

I'm really surprised that it didn't make any difference, JP Magazine recently did two articles on this very idea, one was about a lighter tire and rim combo, the other article was on same tire weight but less aggressive tire tread. The tire tread alone made 1/2 mpg difference.

This maybe a dead end, I'm just trying to get more exploring miles out of a tank and trying to plan trips without so many extra fuel cans strapped on the rack.

Thanks,
Fred
Explorer 1

[reece146]

I don't trust magazine articles: they are written to sell product.

(Edit: switching from a bogger to a high mileage fuel economy tire I could see making a difference - but who wants to run either of those tires on purpose?)

I can't see off-road usage changing much due to tire size... most of it is spent barely tipped into the throttle at all, lots of idling, punctuated by the occasional burst of throttle. Neither aerodynamics or rolling inertia are much of an issue.

I track my mileage via fuelly.com. If there was a difference in mileage it wasn't measurable in the daily grind of driving a vehicle at road speeds on public highways.

If you haven't already, consider opening up the the breathing of the engine. This will help more IME.

[reece146]

Consider importing a long ranger auxiliary fuel tank from Oz? I'll probably do this eventually because I hate carrying gas cans. I'd rather have the fuel under the Jeep and out of the way than tripping over the things.

[eric1115]

Have you considered a 255/85/R16 like the Cooper Discoverer ST? Much milder tread, and the width makes a bigger difference on highway mileage than the weight. It is a little over 33" in diameter, so a little smaller. How are you geared?

[4x4junkie]

I'm really surprised that it didn't make any difference, JP Magazine recently did two articles on this very idea, one was about a lighter tire and rim combo, the other article was on same tire weight but less aggressive tire tread. The tire tread alone made 1/2 mpg difference.

This maybe a dead end, I'm just trying to get more exploring miles out of a tank and trying to plan trips without so many extra fuel cans strapped on the rack.

Thanks,
Fred
Explorer 1

I agree, magazine articles always have to be taken with a grain of salt.
I see it this way: It might take a bit more fuel to get a heavier mass up to speed, but once at that speed, it takes little or nothing additional to keep it rolling at that speed. The added fuel used to get it to speed is infinitesimal compared to the amounts used to overcome wind (aerodynamics) and rolling resistance of the tire.

Raising the air pressure in your tires can help a good amount in lowering rolling resistance (as can tire type), however your aerodynamic profile (combined with the fact most Jeeps aren't the greatest when it comes to MPG to begin with) is going to have a greater effect on your fuel economy. From what I've seen with many friends and their Jeeps, I think the best that can be hoped for is likely to be in the range of 16-18 MPG on the freeway.

[Explorer 1]

I don't trust magazine articles: they are written to sell product.

If you haven't already, consider opening up the the breathing of the engine. This will help more IME.

Thanks, Ive already added one of these that are supposed to help with the breathing at higher speeds along with a bored out throttle body.




I'm using a custom K& N canister filter:



Seems there isn't too much confidence in the JP article........maybe with the weight, height and engine mods, what I'm experiencing is just what to expect.

Thanks,
Fred
Explorer 1