How does fuel economy change with a wider tyre?

[Joe98]

With bicycles, a road bike has a narrow tyre at a high pressure. A mountain bike will have a wide tyre with a much lower pressure. On the road, a mountain bike has a lot of rolling resistance and therefore it is slow v a road bike.

The tyres for the Australian Jeeps are as follows:
The Sport S: 245/75/17
The Willys: 255/75/17
The Rubicon: 285/70/17

All 3 tyres will fit on all 3 vehicles. Note the tyres get wider, namely 245mm, 255mm and 285mm

I presume that as the tyre gets wider there is more rolling resistance hence the fuel economy will decline.

Is there a formula to measure the change in fuel economy?

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[Headbarcode]

The wider a tire gets, the more available traction it will have. More traction equals more friction, thus more rolling resistance.

Yes, there are dozens of mathematical formulas that can be applied to calculating the fuel mileage potential of a specific tire size. Drag coefficient, and whatnot. The problem, no pun intended, is that there are many values needed for those formulas and each one can vary great enough that a larger tire could possibly get better mpg's than a smaller tire in the right conditions.

If you peruse through the what's your fuel mileage threads, you'll clearly see the results of those greatly varying values.

My JLUR is sitting 4" taller than stock suspension, has a decent amount of added weight from upgrades and armor/reinforcements, and is on 40x13.5's. My hand calculated mpg's is 17.1 and consists of 95% stop and go driving. Many have reported the same or less with small lifts and 35's.

Apologies for all this reading and no real answers. Just too many variables that affect repeatable data collecting, so one could turn blue in the face trying to chase it.

Cheers, buddy!

 

[Boatbuilder88]

As @Headbarcode stated, there are many tire variables in play that impact MPGs. Even if you compare the same brand/model tire across the three sizes, the two main variables will be tire width (friction) and tire weight (unsprung weight).

 

[JL MADDOG]

A wider tire may also be heavier, so it adds weight which affects mileage.

Further a wider tire creates just a bit more wind resistance which also affects mileage.

How much that translates into mpg loss is dependent on a lot of variables.

 

[Bohica]

With bicycles, a road bike has a narrow tyre at a high pressure. A mountain bike will have a wide tyre with a much lower pressure. On the road, a mountain bike has a lot of rolling resistance and therefore it is slow v a road bike.

The tyres for the Australian Jeeps are as follows:
The Sport S: 245/75/17
The Willys: 255/75/17
The Rubicon: 285/70/17

All 3 tyres will fit on all 3 vehicles. Note the tyres get wider, namely 245mm, 255mm and 285mm

I presume that as the tyre gets wider there is more rolling resistance hence the fuel economy will decline.

Is there a formula to measure the change in fuel economy?

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