From our experience we have seen that new shoes can make or break the performance of a cyclist. To this extend that at Bioracer Motion we always mention that a bikefit is specific for a certain configuration (Bike, shoes, pedals, saddle), if any of those is changed, you are strongly advised to get refitted. Raymond, co-founder of Bioracer Motion, has done over 10,000 bikefits and he noticed that different shoes have different "hielsprong". This is defined as the extent to which the shoe it tilted upwards at the heel relative to the cleat, when the cleat is placed horizontally. This case study will address the issue by measuring the differences and comparing shoes to each other both on a inter and intra manufacturer level.
Methods and experimental setup
To measure the hielsprong a self-made system was used to secure the shoe. First the flat intermediate piece of a speedplay cleat was attached to the shoe. For the hielsprong measurements, it is important that this part stays flat to be able to measure the hielsprong correctly and in the same way for every shoe. This is done by attaching a piece of wood to the shoe so the shoe can be secured in the plank with the cleat horizontally positioned, see figure 1. After fixing the shoe, a few vertical distances from a point on the outsole, in the neighbourhood of the heel, to the wooden plak are measured. Next the corresponding horizontal distances from the midpoint of the cleat to the point on the outer sole, projected on the plank, are measured. The theorem of Pythagoras allows us to calculate the angle the shoe makes with the horizon. tan (a) = vert. dist. / hor. dist. . The angle is calculated for every couple of horizontal and vertical distances, afterwards the mean is calculated which leads to one angle, one hielsprong (HS), for every shoe, see table 1. The influence of the position of the speedplay cleat is assessed by changing it from totally at the front to the middle and up to the back.
As we can see from figure 1, the shoe is tightly secured at the shoe cleat be mounting it to a piece of wood. This piece fits perfectly well inside the hole and is then tightened up with two screws. There is one piece of measuring tape on the wooden surface, and the height of the shoe is measure with another tool. All measurements were conducted three times to validate, although the measurements are really accurate (within a 1mm error margin).
From Table 1 it can be seen that Bont has a lower "heelsprong" in comparison to Bontrager and Sidi. Table 2 makes the statement even more clear, we see a difference of around 4 degrees between Bont and Sidi and 2.5 degrees between Bont and Bontrager. These differences will have an impact on the cycling movement and general position of the cyclist. This will be addressed in a the next case-study.
Table 3 shows us something even more concerning, between the different manufacturers of cycling shoes, there was no real consensus on what the ideal "hielsprong" is. But even worse, there is not even a consensus for the individual manufacturer, as the different types of shoes also have another "hielsprong". Especially with the Sidi's this is very clear, Bont suffering the least from this. Although their Riot shoe is the odd one out, this is a triathlon specific shoe which has very different characteristics in comparison with the rest of the Bont line.
From the previous figures and tables it can be seen that manufacturers both on an inter and intra manufacturer level do not agree on the correct "hielsprong". It remains uncertain if they know why the "hielsprong" is X degrees for this type of shoes and Y degrees for another. We must note that doing more measurements on different brands of shoes could further improve the reliability of our results. However, it is clear that there is no consensus. These somewhat larger differences (4 degrees) will without a doubt have an impact on the cycling position. Other cleats, like the Shimano road cleats, could even enlarge these differences, as the tests where only done with Speedplay cleats.
This case-study can be a real eye-opener, especially for the pro tour peloton or even every cyclist. In the pro tour peloton, each rider will get new pairs of shoes in het beginning of the new season, and sometimes even during the season. In most cases, the cyclist will not take action to have a new bikefit and can therefore be in a suboptimal cycling position. The case-study clearly shows that there is a need to have another bikefit when you change shoes or pedals. In the next case-study tests will be conducted on how large the differences actually are in terms of cycling movement when you change shoes but do not change your cycling position accordingly. This is the first case-study in a series of eye-openers, these should come in on a monthly basis now, so stay tuned!