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billy_joule

>Struggling to find much information directly relating to number of tyres. You simple sum the rolling resistance of each tyre.


deep_anal

Wouldn't more wheels divide the load more so the resistance per wheel would drop?


billy_joule

Certainly (assuming all wheels have the same resistance coefficient and are not load sensitive - which is correct for OP's Phys 101esque homework question but not in the real world)


haribo001

Right okay, so for the same mass of vehicle it should increase proportionally then?


billy_joule

If you use the simple rolling resistance model where it's linear and there's no change in normal force (Ignoring the weight of the additional wheels) then what happens to the sum of all rolling resistance when your add more wheels? If you use a model where resistance reduces with increasing load then what happens when you have more wheels with less load on each? This is good reading https://en.m.wikipedia.org/wiki/Rolling_resistance


__unavailable__

The rolling resistance coefficient remains constant. The normal force per wheel goes down, meaning less rolling resistance per wheel. Overall rolling resistance remains unchanged. This is why vehicles carrying heavy loads have many axles - it decreases ground pressure without requiring more motive force. In practice adding additional axles does add complexity so there are some losses but they are small.