MPG hit with Toyo AT3s 35x11.5x17 with 3.73s??

[Jerhemi]

I know I lost about 5 mpg going to a MT tire so when these are done all will go back to a AT type

Hmm. Maybe going from stock 32" muds to 35" A/T's will balance out for me haha

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[Gren71]

Hmm. Maybe going from stock 32" muds to 35" A/T's will balance out for me haha

Thats actually an interesting thought. Bigger tires for no real mpg loss would be amazing! Shame it would have to start with already crappy mpg haha

 

[Garemlin]

Hmm. Maybe going from stock 32" muds to 35" A/T's will balance out for me haha

I went from 255/75-17 KM2s to 285/70-17 Kenda Klever AT2s and gained 2mpg.

 

[Mac]

Jeeps obey the same laws of physics as every other vehicle. Turning an engine faster almost ALWAYS results in a higher specific fuel consumption. (gal per hour per hp) The crux of it is whether the motor in the vehicle makes a given amount of power with less fuel by running higher manifold pressure (more torque) and fewer RPMs in a higher gear
or by running lower manifold pressure and higher RPM with lower gearing, it needs to make a given amount of power to move the vehicle down the road.

Why do you think that manufacturers keep putting higher and higher (lower numerically) final drive ratios in vehicles? Its to get better fuel economy. Putting bigger tires makes the gearing taller because the vehicle travels more distance for a given revolution of the tire.

Why does Jeep put lower, higher numerically gears in the JL with the xtreme recon package? Because tires are bigger and the lower gears maintain performance and mileage, same with the Bronco with the Sasquatch package.

 

[Gren71]

Actual clip of every OP when they realize what they’ve done once they bring up tires/gears/mpg

 

[dcmdon]

Why does Jeep put lower, higher numerically gears in the JL with the xtreme recon package? Because tires are bigger and the lower gears maintain performance and mileage, same with the Bronco with the Sasquatch package.

Lower gears maintain performance. Yes.

Mileage - no.

Same with the bronco with Sasquatch package, which gets worse fuel economy than Broncos without it. Because bigger tires and a taller truck takes more power to push down the road at the same speed.

 

[Jerhemi]

I went from 255/75-17 KM2s to 285/70-17 Kenda Klever AT2s and gained 2mpg.

Thats actually an interesting thought. Bigger tires for no real mpg loss would be amazing! Shame it would have to start with already crappy mpg haha

Fine, I will do it....for the science haha

 

[dcmdon]

When you put bigger tires on a Jeep the following impacts push against each other.

Taller tires -> higher gearing = better fuel economy
Taller tires -> more aerodynamic drag = worse fuel economy
Wider tires -> more rolling resistance = worse fuel economy
Heavier tires - > more polar moment of inertia (flywheel effect) = no impact on steady state fuel economy, but impact on efficiency when accelerating or decelerating.

 

[Mac]

Lower gears maintain performance. Yes.

Mileage - no.

Same with the bronco with Sasquatch package, which gets worse fuel economy than Broncos without it. Because bigger tires and a taller truck takes more power to push down the road at the same speed.

I disagree, a JT with 4.10s and 35” tires will get worse mileage than one with 4.56s and 35” tires.

 

[dcmdon]

I regeared a TJ from 3.07 to 4.56 and picked up 2 MPG.

There are rare cases where this could occur. But its rare.

Lets say for example that without re-gearing you are running down the highway in 6th gear most of the time and the motor is turning 3000 rpm.

If you gear down and it allows the transmission to get into 8th and your motor is turning fewer RPM then you could get better economy.

The bottom line is that whatever will keep your RPM at cruise the lowest will get you the best fuel economy. In this example, the best economy would be gained by putting the transmission in manual mode and forcing it into 8th. But I realize that most people wouldn't do that.

Around town there is zero difference because regardless of axle ratio, the transmission will select a gear to give similar RPM at a given speed and load.

 

[Mac]

When you put bigger tires on a Jeep the following impacts push against each other.

Taller tires -> higher gearing = better fuel economy
Taller tires -> more aerodynamic drag = worse fuel economy
Wider tires -> more rolling resistance = worse fuel economy
Heavier tires - > more polar moment of inertia (flywheel effect) = no impact on steady state fuel economy, but impact on efficiency when accelerating or decelerating.

Well aware with how larger tires work with Jeeps I have actually owned a few.

 

[dcmdon]

Well aware with how larger tires work with Jeeps I have actually owned a few.

That's great to hear. But its still relevant to the discussion.

 

[Wheelin98TJ]

There are rare cases where this could occur. But its rare.

Lets say for example that without re-gearing you are running down the highway in 6th gear most of the time and the motor is turning 3000 rpm.

If you gear down and it allows the transmission to get into 8th and your motor is turning fewer RPM then you could get better economy.

The bottom line is that whatever will keep your RPM at cruise the lowest will get you the best fuel economy. In this example, the best economy would be gained by putting the transmission in manual mode and forcing it into 8th. But I realize that most people wouldn't do that.

Around town there is zero difference because regardless of axle ratio, the transmission will select a gear to give similar RPM at a given speed and load.

The TJ was a 3 speed auto. RPM was never lower after regearing.

You're not considering what lugging does to your MPG. Operating in the power band is more efficient.

 

[johnparjr]

Wow. Was that just a change from AT to MT or did you go up in size.?

33 to 35 as well

 

[Orange01z28]

Went from roughly 22mpg with the stock Duelers to 18 with Open Country MTs 35x12.5R17

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