Pedalling Efficiency Rig: Sprung Seatpost Testing
Cycling has evolved into a highly optimised sport, where every watt counts. While aerodynamics often grabs attention, system efficiency, (how effectively a rider’s power transfers through the bike,) is just as crucial, yet frequently overlooked.
The Pedalling Efficiency Rig (PER) at Silverstone Sports Engineering Hub (SSEH) allows performance professionals to isolate individual components, measure rider power versus roller output, and identify power loss and system efficiency. These insights help make informed equipment choices and fine-tune a rider’s setup for optimal performance.
Why Sprung Seatposts Matter
During the spring classics, (races like Tour of Flanders and Paris-Roubaix,) cobbled sectors test frames, wheels, and riders alike. A sprung seatpost could reduce vibration and fatigue over brutal cobbles, but does it improve speed or efficiency?
SSEH used the PER to investigate the impact of a sprung seatpost under controlled conditions, showing how even small component choices affect power transfer and efficiency.
Test Method
This test compared two seat posts (one standard seat post and the other sprung) across different speeds and surfaces.
The baseline tests were conducted on the tarmac roller surface to provide a reference point for each seat post. The speeds for the baseline were 30 kph, 35 kph and 40 kph and tyre pressure was set to 80 psi.
Following the conclusion of the baseline test, the bike was swapped onto the cobbled surface. Both seat posts were tested again at speeds of 30 kph and 35 kph with two different tyre pressures (50 psi and 70 psi).
Each test was completed in the same gear for the respective speed equating to a cadence of 90 rpm.
Results
The baseline data from the initial test conducted on the tarmac roller surface showed that seatpost 1 had a greater power loss and lower efficiency across all speeds compared to seatpost 2. This is shown in Figure 1 & 2.
Figure 1 displays and compares the system power loss between the two seat posts on the tarmac roller surface for the same tyre pressure at three different speeds.
Figure 2 displays and compares the system efficiency between the two seat posts on the tarmac roller surface for the same tyre pressure at three different speeds.
The PER was able to identify differences between seatpost 1 and seatpost 2, and showed that seatpost 1 had a consistently lower power loss across all pressures and speeds on the cobbles when compared to seatpost 2, as shown in Figure 3. This was reflected in the system efficiency measurement which was consistently better in seatpost 1 when compared to seatpost 2 in the same testing conditions. This is shown in Figure 4.
Figure 3 displays and compares the system power loss between the two seat posts on the cobbles for two separate tyre pressures and speeds
Figure 4 displays and compares the system efficiency between the two seat posts on the cobbles for two separate tyre pressures and speeds
Conclusion
Testing with the Pedalling Efficiency Rig highlights how individual components interact within the cycling system. Even subtle differences, such as a sprung seatpost, can shift power loss and efficiency in measurable ways. By isolating these effects, the PER provides a clearer picture of how each part contributes to the overall ride, offering valuable insight into the mechanics of pedalling and bike setup.