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PI ROPE: Polymer fibers make featherweight spokes

The world of cycling is dominated by three materials: steel, aluminum, and carbon fiber, which feature unique properties that make them excel in their specific applications. However, by thinking out of the box there could be other materials that feature enhanced performance, as was the case of ceramics for reduced-friction bearings.

New material in the game

In this quest to exploit different materials, while at the Chemnitz University of Technology, Ingo Berbig started thinking in 2013 about using textile materials like polymers as an alternative to common steel/carbon spokes. With this, he intended to provide a new product based on technological benefits that would lead to improved functionality, from weight to riding feeling, for cycling wheels.

This is how a new concept of spokes made of VECTRAN™ fibers was put into practice and PI ROPE was created in 2017. Not long after, thanks to the cooperation with Newmen Components and a dedicated process of constant self-improvement, they finally commercially launched their first products in 2018. Nowadays, the brand offers a selection of different spokes, hubs, and full wheelsets for different cycling disciplines including road, gravel, and MTB. These represent featherweight wheels with self-damping capacity and similar properties in terms of stiffness, braking load, resilience, aerodynamics, and wear to the commonly used steel.

The science behind the PI ROPE spokes is relatively straightforward. These consist of high-modulus-high-tenacity (HMHT) fibers made out of VECTRAN™, a high-strength polyester fiber used as reinforcement fabric in medicine or space travel applications. On their own, these fibers have similar strengths to steel. However, it is when you braid them that their properties in terms of tension and flexibility are improved, making them excellent candidates as spokes.

Spokes properties

The most remarkable property of the spokes is their reduced weight compared to steel ones, with only 2.2 g. This results in a wheel that can be easily accelerated and is ideal for climbing without sacrificing the functionality of the impeller once the wheel is turning.

The next remark is the spokes look, as they are completely flexible like ropes when not under tension. They are braids of polymer fibers with high flexibility in the transversal direction but a high longitudinal tensile modulus. This results in a spoke that can be certainly put under pressure with reduced elongation and high strength. However, at the same time, the transversal elasticity helps dampen the vibrations transmitted from the ground and provides a smoother riding style.

In terms of wear and exposure to the elements, their properties have been improved to have a long-lasting life. First of all, the fibers do not absorb water and, therefore, no dirt is easily attached. Although these polymers can be easily damaged by the Sun’s UV light, they are covered with a protective coating. Either the dark-colored spokes or the light ones, where fibers can be seen, have 100% protection. There is also no reason to worry about temperature fluctuations, which do not influence the spokes properties of VECTRAN™ in normal riding conditions. Even if you think of them as ropes, they are cut and shatterproof and the external coating avoids wear, tear and creep. Besides, in case of breaking, they can be easily substituted by any experienced wheel builder.

The only downside of the PI ROPE Rope spokes is something they have really thought through. The spokes have relatively larger nipples on both sides, which are used to be attached to both rim and hub. Since the designers did not want to compromise the properties and provide an excellent product, the spokes can only be matched with specific rims and hubs with large holes that do not suit commercial standards. These were produced from the partnership with Newmen Components, developing suitable hubs and rims for the spokes, proving light and extremely reliable in various tests.

Our insight

We had the opportunity to test the R.38 gravel-specific wheelset. Out of the box, we already noticed how light it was. The set is only 1,120 g, achieved thanks to the VECTRAN™ spokes and carbon rims, which have a good balance between deepness and lightness. Then we mounted the discs (centerlock) and tires and went straight to the woods to test them.

After riding on various surfaces (tarmac, dirt, loose gravel) we were surprised by how stiff they were, which was noticeable when doing a small acceleration transmitting all the force with only a small effort. The hub, unlike other brands, was very quiet, which makes you unnoticeable when you are outside.

Finally, regarding the spokes, we could see the braiding of the fibers, since the wheels came with the clear version of the spokes. This is a matter of personal opinion, you may or may not like to give your bike a color touch, but we would have preferred the black ones. Speaking of these, it’s great to always have a spoke on hand, whether in your handlebar bag or jersey pocket, as it takes up very little space and it is easy to replace in the unlikely case of unexpected rupture (although it is really rare).