The Curious Case of the Tired Elliptical Wheel

At the end of last summer I noticed that my bike felt more sluggish, especially when I was tired, but also when I was riding alone, against my own desire for speed. I linked it to changing from Continental GP 5000 to Continental GP 4 Seasons, as well as cooler winter riding, conditions, long leg, and long sleeve layers and riding with an easy group too many times.

A few days ago I rode confidently for over a hundred kilometres. Before the ride I started to hydrate, and then I hydrated for the entire ride. The result is that when I was at the Emil Frey traffic light I was fresh enough to push. The issue is that the chain jumped from the rear cassette to the wheel spokes, and then got jammed.

The reason it got jammed, according to AI, and my own belief that the logic is sound, is that the wheel spokes, fatigued by years of use were already less rigid than they should be. This is key, as I will explore now.

I noticed, when solo riding, and when riding with groups, that whereas before I kept up with a group with ease, and everyone else did, I was suddenly more sluggish. I would put out power but I felt as if something was damping the effort. I checked the brake alignment but that wasn’t it. I considered the tyres, and when I switched from GP 4S to 5k I noticed an improvement.

The problem is that at the end of rides the bike felt more sluggish, as if it was resisting my efforts to advance. I considered clothing, tyres, season. What I didn’t consider was wheel spoke fatigue.

The concept is simple. Before each ride we inflate the tyres, to ensure that they are at the pressure we want. This maximises power transfer from the wheel to the road. What I didn’t consider was a “softer” wheel.

As the spokes get older, and shaken around, with each rotation of the wheel, so they get fatigued and distend. Over time that distention results in the wheel going from “static” to dynamic. These are not the right terms, but they illustrate the idea.

If you have a mountain bike, that you use on roads, and you’re climbing up a hill, then you harden the suspension to make it as rigid as the suspension will allow. In so doing the bike transfers the power to moving forward, rather than loading a spring.

My rear wheel became a spring of sorts. When I was fresh, and full of energy I rode, and my freshness offset the watts that I was losing through the wheel. The wheel was absorbing the energy I was putting out, rather than sending it directly to the road.

That’s why, when others were riding fast, I could keep up, but then burned out. I could feel the ‘drag’ but I didn’t know that the fatigue I felt was due to the wheel.

We hear about oiling/waxing chains, inflating tires, but we hear less often about checking wheel spokes for tension.

And Finally

I could feel that something wasn’t right. It’s a shame I didn’t have the reflex to test the wheel spokes for both wheels. I would have diagnosed the issue sooner.