Miles/gallon: Newer vs Older Cars

[daliant]

Can anyone explain how the wide big rig tires for the Smart Way program have less rolling resistance than two smaller "dually-style" tires? It seems like there'd be more resistance due to the larger contact patch. Any truckers on this site?

I think it has more to do with the super single setup weighing less than the traditional dual wheels, 10 wheels and tires vs 18, less weight = better mileage BUT the rig is still going to weigh as close to #80000 as possible to stay legal while hauling the most material down the road, so it will likely end up being a case of number fudging to enhance the perceived value of a product.

 

[MRGTX]

Can anyone explain how the wide big rig tires for the Smart Way program have less rolling resistance than two smaller "dually-style" tires? It seems like there'd be more resistance due to the larger contact patch. Any truckers on this site?

Not a trucker but here's my guess:

A lot of the rolling resistance of a tire comes from the compression of the sidewall which happens like a "wave" as the tire rolls.

The section that is pressed against the ground is always bulged slightly...and that flexing requires energy.

If you have two fewer sidewalls to flex, you'll save a lot of that energy. This is probably offset a little bit by the greater contact patch and more flexing of the remaining sidewalls...but there's certainly a net energy saving.

 

[MopaR&D]

I would guess it also has to do with cost, one larger tire and wheel is still a lot cheaper than 2 smaller tires and wheels. Also just from memory of seeing big rigs on the road with dually vs. wide single tires, if you add the contact patch of the two tires together it's not much less than the one wider tire. The overall contact area needs to be above a certain amount anyway in order to support all that weight and not overload the tires.

 

[Tadams]

In an 18 wheeler, if you can use the single tire and wheel you are saving weight which allows you the ability to haul more weight. Been there done that in a previous life. Drove in all 48 continental states and Canada.

 

[Tadams]

In my Barracuda, I think I will measure smiles per gallon a lot more than miles per gallon anyway.

 

[pishta]

Smart fuel management on the wideband cars can also lean cruise down to as much as 18:1 with huge amounts of EGR. thats like 25% lower fuel used for that type of driving as well as idle.

 

[ab7fh]

I know new technology helps, but were the older cars just a lot more inefficient? Where have the main improvements come from?

Electronic engine management, lock up torque converters, OD transmissions, and aerodynamics are the biggies.