Validity of a device designed to measure braking power in bicycle disc brakes

Abstract

Real-world cycling performance depends not only on exercise capacities, but also on efficiently traversing the bicycle through the terrain. The aim of this study was to determine if it was possible to quantify the braking done by a cyclist in the field. One cyclist performed 408 braking trials (348 on a flat road; 60 on a flat dirt path) over 5 days on a bicycle fitted with brake torque and angular velocity sensors to measure brake power. Based on Newtonian physics, the sum of brake work, aerodynamic drag and rolling resistance was compared with the change in kinetic energy in each braking event. Strong linear relationships between the total energy removed from the bicycle-rider system through braking and the change in kinetic energy were observed on the tar-sealed road (r = 0.989; p < 0.0001) and the dirt path (r = 0.952; p < 0.0001). T-tests revealed no difference between the total energy removed and the change in kinetic energy on the road (p = 0.715) or dirt (p = 0.128). This study highlights that brake torque and angular velocity sensors are valid for calculating brake power on the disc brakes of a bicycle in field conditions. Such a device may be useful for investigating cyclists' ability to traverse through various terrains.

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

“…Two cyclists (178.0 and 172.0 cm; 85.04 and 73.60 kg) completed 100 braking trials across three days on a mixture of flat, gravel roads and flat, paved roads while riding a bicycle outfitted with a validated brake power meter (Figure 1) at both the front and rear brakes of the bicycle (Miller et al, 2017a). For the functioning of this brake power meter, hollow aluminium blocks (Figure 1A) were fitted to a mountain bike on the standard brake caliper mounting posts.…”

“…Until recently, it has been impossible to quantify efficiencies in bicycle riding outside of propulsive and physiological variables. However, a bicycle brake power meter has recently been validated that can measure the rate of energy removed from the bicycle rider system through the rider-induced interaction between the brake caliper and the rotor (Miller et al, 2017a). This brake power meter has since been utilised to calculate the brake work and rate of brake work (brake power) during actual cycling (Miller et al, 2018a;Impellizerri & Marcora, 2007).…”

“…The first published study using a brake power meter introduced the importance of measuring braking during cycling and then went on to validate energy losses due to braking when compared to the change in kinetic energy of the bicycle-rider system (Miller et al, 2017a). Later, an initial descriptive study in braking during XCO-MTB supported evidence that propulsive power was important for a high level of performance, but purported that analyses of performance were enhanced with the addition of a brake power meter (Miller et al, 2018a).…”

“…The total duration of this skidding equated to 1.1 s per lap on a 1.24 km crosscountry mountain bike race track (Miller et al, 2018a). While the benefits or detriments of skidding and performance are not well-understood, previously described methods (Miller et al, 2017a;Miller et al, 2018a;Miller et al, 2018b) utilised to calculate brake power were not able to account for friction-related energy losses experienced when the rear wheel is skidding. In these investigations, brake power (PB) was calculated at each brake as the product of brake torque times the angular velocity of the wheel given,…”

Thermal/Mechanical Measurement and Modeling of Bicycle Disc Brakes

“…A transient model of component heating is useful to understand the thermal dynamics and component temperatures. The automotive industry has long ago accepted the benefits of brake thermal modeling and testing [1], and there have been recent efforts to test bicycle brakes on a test bench [2], and to measure brake power during outdoor trials [3]. The focus in this work is to develop a bicycle disc brake thermal model and to provide experimental validation of its predictive capability in a laboratory environment.…”