With a twang, a rattle and a horrible ripping sound, RCUK’s current test of Rolf Prima’s Aspin wheelset came to a sudden halt. Well, actually, it didn’t. Amazingly, despite the high tension and low number of the rear wheel spokes, the loss of one of them did not throw the rim so far out of true as to make the wheel unrideable. Indeed, so true did the wheel remain that I was at a loss initially to explain the noises, which erupted as I crested West Peckham’s hill on the Sydenham Wheelers reliability trial.
So, what happened? Here is a classic example of a spoke that has fatigued and cracked at the rim. Spoke fatigue failure is probably more usual at the hub, but a well-built wheel will have spokes that have been “seated” against the flange to remove residual curvature and its associated flex during riding.
A tangent-laced spoke enters the rim at a slight angle. Conventional spoke nipples allow some self-alignment, but those in the Rolf Prima Aspins sit inside the rim, obliging the spoke to kink slightly on exit. It is this kink that may flex minutely with each power stroke and this, allied perhaps to some corrosion, is likely to be the reason the spoke broke.
Fortunately, while I was still riding the loose spoke managed to wrap itself around another and then jam under the rim, meaning I could carry on the the finish without having to lose time effecting a bush repair. But, since the hidden nipples prevent easy tweaking, seems my reservations concerning using these hoops for the autumn tour were well-founded.
Whether this is a problem inherent in the way the spokes enter the rim is hard to say without many more miles. This breakage happened after some 1500 of them in all conditions during which the wheels otherwise distinguished themselves with an exceptionally pleasing ride quality, excellent power transfer and impressively true running. What next? I hope to fit a new spoke and continue the test, in which case we’ll be able to see how the remainder get on.
Rolf Prima Aspin wheelset £450