What is rolling resistance caused by?
Rolling resistance is caused by the deformation of the tire and the road surface as the wheel rolls. Energy is lost due to hysteresis in the tire material, surface irregularities, and internal friction within the tire structure. See also our Wheel Size Calculator (Plus Sizing).
How do I calculate rolling resistance force?
Rolling resistance force is calculated using the formula: RR = Crr × N, where Crr is the coefficient of rolling resistance and N is the normal force (weight pressing down on the tire). The coefficient varies based on tire type and surface conditions.
What are typical rolling resistance coefficients?
Typical coefficients range from 0.003-0.015 for bicycle tires, 0.008-0.015 for car tires, and 0.006-0.012 for truck tires. Racing bicycle tires on smooth surfaces can achieve coefficients as low as 0.003, while mountain bike tires on rough terrain may exceed 0.020.
How does tire pressure affect rolling resistance?
Higher tire pressure generally reduces rolling resistance by minimizing tire deformation. However, excessively high pressure can increase vibration losses and reduce comfort. The optimal pressure balances rolling resistance, comfort, and grip.
Does rolling resistance depend on tire size?
Rolling resistance force doesn't directly depend on tire size, but rather on the load and coefficient. However, larger tires typically have lower rolling resistance coefficients due to reduced deformation, while wider tires may have slightly higher coefficients.
How much power does rolling resistance consume?
Power consumption depends on speed and rolling resistance force. At cycling speeds (20-30 km/h), rolling resistance typically consumes 20-40% of total power output. At higher car speeds, aerodynamic drag becomes more dominant than rolling resistance.
Can low rolling resistance tires improve fuel economy?
Yes, low rolling resistance tires can improve fuel economy by 2-8% in typical driving conditions. The improvement is most noticeable in city driving and at moderate speeds where rolling resistance is a significant portion of total resistance. You might also find our calculate Tire Speed Rating Chart useful.