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What does weight matter on a road trip? Unless you are exclusively driving at 30 mph uphill I don't see it mattering much. Wind resistance is the dominant force

What does weight matter on a road trip? Unless you are exclusively driving at 30 mph uphill I don't see it mattering much. Wind resistance is the dominant force. This is the same reason why most railroads put limitations on the maximum grade they have to climb. They are mainly working against wind resistance, not gravity.

apexalpha 3y ago
>Wind resistance is the dominant force. Hence, smaller cars have better MPG. Smaller cars also tend to be lighter.
aidenn0 3y ago
There are two numbers on the sticker for fuel efficiency. In-town and highway. For in-town weight matters greatly (both because you essentially throw away energy every time you break, and because rolling-resistance matters more at low speed). For highway, up until 2008 the maximum speed tested was 55, which disadvantages heavy-vehicles, as rolling resistance is a higher component of energy used at lower speeds (as a simple approximation, rolling-resistance is linear, and air-resistance is quadratic).
- sidewndr46 3y ago
  The thread was specifically about a road trip. I can't imagine anyone taking a road trip entirely in town.
  - aidenn0 3y ago
    I've done road-trips entirely off of limited-access highways.
  - bialpio 3y ago
    Driving around Yosemite or Yellowstone is gonna be closer to in-town riding than to highway riding. I wouldn't be too surprised if time spent on driving at the destination was ~50% of my driving time at some road trips I took.
jusssi 3y ago
Heavier vehicle puts more work into deforming the road. It must follow it also puts more energy into that.
_Microft 3y ago
Road damage scales with fourth power of axle load. A car that is 50% heavier does 5 times the damage. https://en.m.wikipedia.org/wiki/Fourth_power_law https://en.m.wikipedia.org/wiki/Fourth_power_law
- sidewndr46 3y ago
  The thread was about fuel economy on a road trip.
Symbiote 3y ago
Railways have very low gradients due to the limits of friction of steel wheels on steel rails.

apexalpha 3y ago

>Wind resistance is the dominant force. Hence, smaller cars have better MPG. Smaller cars also tend to be lighter.

aidenn0 3y ago

There are two numbers on the sticker for fuel efficiency. In-town and highway. For in-town weight matters greatly (both because you essentially throw away energy every time you break, and because rolling-resistance matters more at low speed). For highway, up until 2008 the maximum speed tested was 55, which disadvantages heavy-vehicles, as rolling resistance is a higher component of energy used at lower speeds (as a simple approximation, rolling-resistance is linear, and air-resistance is quadratic).

sidewndr46 3y ago
The thread was specifically about a road trip. I can't imagine anyone taking a road trip entirely in town.
- aidenn0 3y ago
  I've done road-trips entirely off of limited-access highways.
- bialpio 3y ago
  Driving around Yosemite or Yellowstone is gonna be closer to in-town riding than to highway riding. I wouldn't be too surprised if time spent on driving at the destination was ~50% of my driving time at some road trips I took.

jusssi 3y ago

Heavier vehicle puts more work into deforming the road. It must follow it also puts more energy into that.

_Microft 3y ago

Road damage scales with fourth power of axle load. A car that is 50% heavier does 5 times the damage. https://en.m.wikipedia.org/wiki/Fourth_power_law https://en.m.wikipedia.org/wiki/Fourth_power_law

sidewndr46 3y ago
The thread was about fuel economy on a road trip.

Symbiote 3y ago

Railways have very low gradients due to the limits of friction of steel wheels on steel rails.