Calculation of rear brake power and rear brake work during skidding on paved and gravel cycling surfaces

Abstract

The use of a brake power meter at each wheel of a bicycle is a valid means to calculate energy losses due to braking. However, methodology utilizing the torque and angular velocity at each wheel independently are not able to reflect energy lost to braking when the rear wheel is skidding. This study tested the possibility of using the angular velocity of the front wheel, but the torque of the rear brake, to calculate rear brake power. Two cyclists completed 100 braking trials across three days on a mixture of paved and gravel surfaces with a mixture of skidding and non-skidding. The estimated total energy removed from the bicycle-rider system was calculated as the sum of brake work and estimates of drag and rolling resistance. This energy removed from the bicycle-rider system displayed a strong positive relationship with the change in kinetic energy of the bicycle-rider system during braking on paved (r²=0.955; p<0.0001) and gravel surfaces paved (r²=0.702; p<0.0001). There was no difference between these measurements overall (p<0.05), however there is some error of measurement when skidding on gravel. The findings in the present investigation indicate that rear brake work is underestimated when using the angular velocity at the rear wheel during skidding, but that utilising the angular velocity of the front wheel is a valid means of calculating rear brake power. Care should be taken when skidding on gravel as it is difficult to assess the linear velocity of the bicycle.