Rolling Friction Article Index for
Rolling 		Website Links For
Rolling 		 

Information About

Rolling Friction
  CATEGORIES ABOUT ROLLING RESISTANCE
   
classical mechanics
   
introductory physics
   
tires
   
SHOPPER'S DELIGHT
 
Shop For:  
Department
Price Minimum:
Price Maximum:
      



It is worth noting that for all vehicles that travel upon Wheel s (such as cars and Bicycles ), the sum of rolling friction and Static Friction is what causes the vehicle to slow when the Brake s are applied. The actual force applied in braking (for example, clamps applied to Disk Brake s) is internal, and by Newton's First Law cannot cause a change in the vehicle's motion. Therefore the slowing is caused by contact between the road and the car's tires; the Static Friction force between road and tire is the "equal and opposite reaction" specified in Newton's Third Law . Rolling friction can be compared to Sliding Friction , as when the brakes "lock up", they slide upon the driving surface and do not sufficiently slow the car. Maximum braking force occurs when there is about 11% slip between the wheel's speed and the road - this is used to advantage in ABS braking systems, and Cadence Braking , a manual technique which achieves something similar.

Several factors affect the magnitude of rolling friction a tire generates:
  • Material - Tires with higher Sulfur content tend to have a lower rolling friction. This is one strategy that most hybrid car vendors use to improve fuel efficiency.

  • Dimensions - rolling friction is proportional to the contact area of the tire - so a thinner tire will exhibit less friction (but also less grip) than a wider one.

  • Extent of inflation - Partially inflated tires tend to suffer higher rolling friction. This may lead to overheating and may have played a part in the infamous Ford Explorer Rollover Accidents .

  • Hard rail steels last longer but may also have lower Static Friction . They may also suffer Fatigue Cracking because the cracked area is not worn away by the passing Train s.


Rolling resistance is generally measured in Crr , and ranges from 0.0028 for a bicycle with Michelin Ecorun bicycle tires up to around .05 for earth-moving equipment[http://www.eng-tips.com/viewthread.cfm?qid=90548&page=1 .


EXTERNAL LINKS