# Rolling Resistance

Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface. The torque to overcome this resistance and maintain steady speed on level ground (with no air resistance) is just this resistance multiplied by the radius of the wheel.

It is mainly caused by non-elastic effects, that is, not all the energy that is needed for deformation (or movement) of the wheel, roadbed, etc. is recovered when the pressure is removed. Two forms of this are hysteresis losses, see below, and permanent (plastic) deformation of the object or the surface (e.g. soil). Another cause of rolling resistance lies in the slippage between the wheel and the surface, which dissipates energy. Note that only the last one of these effects involves friction, therefore the name "rolling friction" is to some extent a misnomer.

In analogy with sliding friction, rolling resistance is often expressed as a coefficient times the normal force. This coefficient of rolling resistance is generally much smaller than the coefficient of sliding friction.

Any coasting wheeled vehicle will gradually slow down due to rolling resistance including that of the bearings, but a train car with steel wheels running on steel rails will roll farther than a bus of the same mass with rubber tires running on tarmac. Factors that contribute to rolling resistance are the (amount of) deformation of the wheels, the deformation of the roadbed surface, and movement below the surface. Additional contributing factors include wheel diameter, speed load on wheel, surface adhesion, sliding, and relative micro-sliding between the surfaces of contact. It depends very much on the material of the wheel or tire and the sort of surface it runs on. For example, a rubber tire will have higher rolling resistance on a paved road than a steel railroad wheel on a steel rail. But if one were to drive a steel wheeled vehicle on a paved road it would likely have more resistance than a rubber tire would. Also, sand on the ground will give more rolling resistance than concrete.

### Other articles related to "rolling resistance, resistance, rolling":

Comparing Rolling Resistance of Highway Vehicles and Trains
... While the specific rolling resistance of a train is far less than an automobile or truck in terms of resistance force per ton, this does not ... Thus one needs to know the rolling resistance per passenger (or per net ton) to make such comparisons ... To find the rolling resistance per person one multiples the pounds(force) per ton (2000 times the rolling resistance coefficient) by the tons per passenger ...
SAE J2452
... SAE J2452 is a standard defined by the Society of Automotive Engineers to define the rolling resistance of tires ... The rolling resistance coefficient (RRC) indicates the amount of force required to overcome the hysteresis of the material as the tire rolls ... and velocity all play a role in how much force is lost to rolling resistance ...
Automobile Handling - Factors That Affect A Car's Handling - Unsprung Weight
... However, the compressive resilience of the tire results in rolling resistance which requires additional kinetic energy to overcome, and the rolling resistance is ... To reduce rolling resistance for improved fuel economy and to avoid overheating and failure of tires at high speed, tires are designed to have limited internal damping ...
Solar Car Racing - Vehicle Design - Performance Equation
... the right hand side is the energy needed to drive the car along the race route (overcoming rolling resistance, aerodynamic drag, going uphill and accelerating) ... payload (newtons) 2400 ... Crr1 First coefficient of rolling resistance (non-dimensional) 0.0060 0.0050 0.0027 0.0027 Crr2 Second coefficient of rolling ...
Solar Car Racing - Vehicle Design - Rolling Resistance
... Rolling resistance can be minimised by using the right tires, inflated to the right pressure, correctly aligned, and by minimising the weight of the vehicle ...

### Famous quotes containing the words resistance and/or rolling:

The aim of every political association is the preservation of the natural and imprescriptible rights of man. These rights are liberty, property, security and resistance to oppression.
—French National Assembly. Declaration of the Rights of Man (drafted and discussed August 1789, published September 1791)

... in the cities there are thousands of rolling stones like me. We are all alike; we have no ties, we know nobody, we own nothing. When one of us dies, they scarcely know where to bury him.... We have no house, no place, no people of our own. We live in the streets, in the parks, in the theatres. We sit in restaurants and concert halls and look about at the hundreds of our own kind and shudder.
Willa Cather (1873–1947)