Weight or Diameter? Biggest MPG killer

[yumave]

Ive searched and havent found a thread so here it goes
I have a stock mojave with the lt285/70R17 falken m/t which weigh in at 60lbs

will i see improved mpg by going with factory lt285/70R70 falken a/t which come in at 62lbs??

how much different is the rolling resistance of the mt compared to the at?

now the biggest question
Whats the biggest mpg killer
heavier same diameter tire or bigger diameter same weight tire?

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[yumave]

Only video ive found with some info but not all my answers

 

[Garemlin]

If you don't want to go bigger you should consider the Kenda Klever AT2s in P285/70-17. They weigh in at 46lbs each.

 

[yumave]

Not bad!

 

[Kevin_D]

Weight: a heavier tire will take a bit more energy to get it rolling, but once rolling it’ll have more inertia, and therefore a greater tendency to stay rolling. 10-15 lbs. per tire is an insignificant fraction of the weight of the truck, so it won’t noticeably effect fuel consumption. More unsprung weight will effect handling performance, but we’re talking a Jeep, not some hyper-performance sedan.

Diameter: a larger tire will effectively lower your final drive ratio (think 4.10 to 3.73,) and while it will tend to reduce performance, it’ll also tend to improve economy. More distance traveled per tire revolution.

Kevin

 

[rob_o]

40s on beadlocks, about 135lbs per wheel.

 

[MPMB]

Weight: a heavier tire will take a bit more energy to get it rolling, but once rolling it’ll have more inertia, and therefore a greater tendency to stay rolling. 10-15 lbs. per tire is an insignificant fraction of the weight of the truck, so it won’t noticeably effect fuel consumption. More unsprung weight will effect handling performance, but we’re talking a Jeep, not some hyper-performance sedan.

hehe.

unsprung weight affects performance at a multiple. 3x. So your 15# per tire is 60# x 3 = 180# of weight that the engine has to move.

Weight plays a huge role. That 180# may not seem like much, but it's on the part of the vehicle that is more sensitive.

 

[whiteglad]

I chose 255-80-17E Falken AT3W, which are 10 lb each lighter (52 vs 62 lb) than the Rubi/Mojave size, slightly (0.3") taller, and also 1" narrower being stock width of the max tow tires they replaced. After adjusting the speedo/odo, mpg is the same as with the 34 lb stock tires that were 31.5". I don't know if I can make any strong conclusions, but moderately more height and some more weight with same width did not hurt in my case, with 4.10 ratio. I can also say that the KM mudders on my JKU were noisy and gave lower mpg than milder tread pattern tires.

 

[bleda2002]

Going from 33 to 37 but almost same weight I think most of my mpg loss was more me trying to keep driving like I did before and using more gas pedal

 

[Delhux]

40s on beadlocks, about 135lbs per wheel.

Nice!

Whats your gear ratio?

 

[cdyoung9799]

40s on beadlocks, about 135lbs per wheel.

Wow!

 

[rob_o]

Nice!

Whats your gear ratio?

4.10

 

[Blade1668]

Going from 33 to 37 but almost same weight I think most of my mpg loss was more me trying to keep driving like I did before and using more gas pedal

Hit it on the head. The application of the two pedals on the floor. Gas and braking. Jackrabbit starts n stops plus hauling tail if I keep it at 50-65 I gain 5 plus mpg. Local driving conditions will have a effect with heavy tires if hills and "City" driving conditions.

 

[rob_o]

I just want to point out my acceleration is noticeably slower, but I don't exactly drive like a race car driver to begin with.

basically instead of shifting at 2200-2500 it won't shift until 3k now. not the biggest deal.

it still has plenty of power to pass people at freeway speed

 

[ShadowsPapa]

No one considered rolling resistance - the friction of a wider tire on the pavement vs. the standard width, the more aggressive tread being harder to roll, etc.
I see where weight is considered - and it's said that a heavier tire will be harder to get rolling but not so bad to keep rolling...... well, unless you always drive with cruise on and it never changes speed or never goes up an incline (the engine must lift the truck up that hill - tires and all) yes, the weight does matter. The mass, thus inertia, only doesn't matter if you are flying a perfectly straight line and perfectly steady speed.
Otherwise yes, the mass matters for multiple reasons.
I moved from H/T to A/T tires of the same diameter, a bit wider, and saw a loss in MPG - and the dealer that sold me the tires "warned me" although I told him I was aware - I wanted better tires for our nasty weather. I knew it would drop some - and it did - SAME diameter, same weight!

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