Pedalling Efficiency Rig: Sprung Seatpost Testing

Introduction

In recent years cycling has become increasingly optimised in the pursuit of performance.

Aerodynamics is often the first point of interest when considering optimisation, however, system efficiency can be just as important and is regularly overlooked.

Using the Pedalling Efficiency Rig (PER) at Silverstone Sports Engineering Hub (SSEH), individual components of a system can be isolated to identify power output from the rider and compare it to the output power of the roller, providing system efficiency and power loss. This information can then be used to make informed equipment choices and optimise a rider’s setup.

Trivia

During the spring professional cyclists take on the legendary spring classics. Races like The Tour of Flanders and Paris-Roubaix are well known for their savage cobbled sectors which have lain waste to many frames and wheels over the years.

If a professional rider had the option to install a sprung seat post to their bike to dull the brutal cobbles of Arenburg Forest, they would likely request it without hesitation. But is it any faster? SSEH conducted a study to find out.

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