Pedalling Efficiency Rig – Rolling Resistance

Introduction

In cycling, it is well established that aerodynamic drag has a significant contribution to an athlete’s resistance.

However, in the pursuit of performance, we must consider not just the drag of the athlete and their equipment, but the losses in efficiency from the drivetrain, mechanical properties of the frame, as well as rolling resistance of the tyres, creating a whole system loss.

The Pedalling Efficiency Rig (PER) at Silverstone Sports Engineering Hub was used to carry out this investigation. The PER measures the power input of the athlete vs the power output of the roller (useful power, propelling the rider forward at the road surface). From these values, the PER can quantify the losses and state it in terms of efficiency or absolute power loss. A change in the system setup will be noted as a change in efficiency, allowing for the optimisation of equipment choices.

Test Method

A speed sweep was carried out between 8m/s and 12m/s, at 1m/s increments, with a sample time of 30 seconds. The tyre pressure was kept at 110psi. The chain tension was kept the same and a fixed gear bike was used to ensure no change in chain alignment.

The participant ramped up to 8m/s and when at a constant velocity, the first sample was run. Once the sample time was complete, the participant ramped up to the next velocity. The participant remained on the bike for the duration of the speed sweep from 8m/s to 12m/s.

The speed sweep was carried out across a baseline tyre and four other tyres. The baseline tyre was repeated at the end of the data collection to ensure there was no deviation from the first run.

Results

In the speed sweep, the PER was able to measure a noticeable difference between the five tyre samples. As seen in the graph below, there is a consistent offset between the tyres. Tyre 1 has the lowest power loss across all speeds and Tyre 3 had the highest power loss across all the speeds. Each of the tyres followed a similar trend, with greater power loss at higher speeds. Plotted lines of power loss vs road speed followed a similar offset between samples. Tyre 2 and Tyre 5 performed similarly together across all speeds.

Writing these observations in terms of efficiency: Tyre 1 was the most efficient and Tyre 3 was the least efficient across all the speeds. Tyres 2 and 5 performed similarly to each other. As the speed increased, so did the efficiency of the tyre, indicating that they all performed better at faster speeds.

Conclusion

The results from the test provide clear evidence that there is potential to find a significant reduction in rolling resistance and therefore improve system efficiency when selecting the right tyre for your target event.

If you would be interested in arranging a session on the Pedalling Efficiency Rig to optimise your own equipment choices, please get in touch via email info@silverstonesportshub.co.uk or via phone 01327 222830.