How Much Does Weight and Rolling Resistance Affect Gas Mileage?

[Dweano]

Well...I'm looking to upgrade to 35x12.50x15 from 33x12.50x15. Right now I have Toyo Open Country M/T's. In an earlier thread about gas mileage everyone said ditch the heavy toyos and get a lighter tire to help with mileage. Well heres some stats:

Toyo (33x12.50x15...what I have now): 69 pounds
Bfg Km2 Muds (35x12.50x15): 61 pounds
Bfg All Terrains (35x12.50x15): 54 pounds

So really...I do have heavy tires now...but even the bigger bfg muds are only 8 pounds lighter...times 4 for a total of 32 pounds less of rotational weight. Then 7lbs (28) total less for the all terrains...but how much does that really play into the overall gas mileage?

I was going to go with all terrains but for only 7 more pounds per tire I could have mud tires still...choices choices!

 

[bcost882]

if you actually use the mud tires don't get the BFG A/Ts cause they are crap in mud frum everyone and every experience i have. but if you just occasionally offroad you do not really need M/ts if you are not a big mud person

 

[kimcrwbr1]

I guess it is all relevant to your carbon footprint. he he sorry I just had ta It all depends on the skinny pedal and the weight of your foot the bigger the tires the heaver your foot needs to be. I dont think the weight of the tires has alot to do with the figure the higher you can get the rpms (gears) the less you will need on the throttle.

 

[nate09]

i went from a 235/75 AT to a 30/9.5 MT during the winter time and have been checking my fuel mileage every tank. thus far i havent seen a significant drop in mileage having changed tires, at most 1 or 2 mpg.

 

[Dweano]

Yeah I dunno. I'm thinking I will stay with mud tires. The thing is I can go for months without taking it off the road (usually in summer) but then all of a sudden I'll need to go to a really muddy place to pull out my friends or something haha. In winter I like hacking thro snow and stuff. I am kinda tempted to get two sets of tires. Muds for winter and spring, and then ATs for summer and fall. Even a 2mpg difference is quite a bit. Thats like 10%

 

[Jason]

What do you use the truck for? Mud tires suck for everything but mud. Living in the northeast I drive on it all. I have mud tires, but they are separate rims and only go on for mud.

 

[bcost882]

thats a good idea^^^^

 

[nate09]

i can average anywhere between 17-20 per tank, so it really just depends on what kind of driving im doing. sometimes im doing mostly highway driving, other times im pulling a trailer. as far as losing mpg, i havent noticed enough of a difference, a slight loss of power due to horrible gearing but i dont regret going with a m/t.

 

[strvger]

you will loose mileage and power due more to the width of those big tires and their relatively low tire pressure, rather than their weight.
that is why i run tall, skinny, E rated AT style tires on my truck. i can run them at 45-50psi (or more) for the long trips on the freeway and lower the psi for around town driving. harder tires = lower rolling resistance and higher mileage. on smooth freeways, the ride isn't too bad.
keeping the over all width under 10" means catching less wind while they are rolling and less power/mileage loss. my tires fit under my fenders and allow the wind to flow around the body for the least resistance.
my chosen tires are great in snow, superior on winter ice, and quite capable in spring mud up to 6-8" deep.
just my $.02.

 

[Dweano]

So really theres no disadvantage to running a mud tire? Except bad handling and stuff...which I don't really care about cuz I drive gravel that throws me around anyways...if I got a mud tire that I could run highish PSI I would get better mileage your saying?

 

[strvger]

don't think i said that exactly. but i did forget something. a lot depends on your gearing. if you are running higer (like 3.45) gears with big, wide tires, you will have your foot deeper in the gas pedal for the needed power. if you are running lower ( like 4.56) gears with those same big, wide tires, you will need less throttle. but in any event, you will not get get excellent fuel economy running grossly oversized tires on your truck no matter their weight, tread type, gearing, or tire pressure.

 

[Dweano]

don't think i said that exactly. but i did forget something. a lot depends on your gearing. if you are running higer (like 3.45) gears with big, wide tires, you will have your foot deeper in the gas pedal for the needed power. if you are running lower ( like 4.56) gears with those same big, wide tires, you will need less throttle. but in any event, you will not get get excellent fuel economy running grossly oversized tires on your truck no matter their weight, tread type, gearing, or tire pressure.

Haha yup yup I know all that. 4.56s are going in soon...but I'm talking just tires here. "you will not get get excellent fuel economy running grossly oversized tires on your truck no matter their weight, tread type, gearing, or tire pressure"...but whats the least worst tire for mud tires then? Would it be the lightest, or the one that you can inflate to the highest psi? Or a combo of both? ...hmm...I think I am entering the quest for the perfect tire haha

 

[triumphrider-1]

Haha yup yup I know all that. 4.56s are going in soon...but I'm talking just tires here. "you will not get get excellent fuel economy running grossly oversized tires on your truck no matter their weight, tread type, gearing, or tire pressure"...but whats the least worst tire for mud tires then? Would it be the lightest, or the one that you can inflate to the highest psi? Or a combo of both? ...hmm...I think I am entering the quest for the perfect tire haha

It could be either tire really. The weight of the tire makes the most noticeable difference upon acceleration and decceleration (you got to get the momentum going/stopping). So the heavier tire will suck more in that respect (as has been mentioned).

As far as traveling steady state, a heavier tire will carry/require more load than a lighter one, but the tires also have different Rolling Resistances too. The tires with higher RR will have greater effect on the fuel economy than those with less RR. Generally speaking, a mud terrain tire will have a higher RR than an all terrain tire.

The lighter tire will also be better for the suspension cycling at "high speeds" (above 30mph), but you said you don't really care about that.

 

[01_ranger_4x4]

iwould stay with the mud tires really. i just went from 33X10.5 BFG AT's to 33X12.5 BFG KM2's and ive noticed no difference in mileage between the two.

 

[Jason]

You'll notice they suck for grip on pavement AND wear out faster.