Originally Posted by
grolby
Good post. I don’t agree with this, though - rim strength is clearly very influential in the overall strength of a wheel. The existence of stiffer, more heavily built touring rims back in the day wasn’t merely an exercise in marketing. They really do help. I think this is completely consistent with your explanation of spoke fatigue, above: a stronger, stiffer rim will presumably deflect less on impact and impart less force to the spokes as a result. In the old days of course you basically had to pick: light but weak, or strong but heavy. Modern manufacturing means we can now have our cake and eat it too, at least to an extent. Of course a high spoke count with that strong rim is the best of all worlds. Still, even modern 24 and 28 hole road racing rims are amazingly strong. On sheer reliability per dollar, I’m not sure anything will ever compare to the 36 hole Rhyno Lite wheels I had on my LHT 15 years ago, but I wouldn’t hesitate now to go on the road for a week with the same wheels I ride and race road and cyclocross with.
The problem is that the “stronger, stiffer” rim doesn’t have anything that makes it stronger nor stiffer. If you look at the profiles of the rims, the rims that are supposedly “stronger” don’t have any thicker material. They are usually wider or taller but they use the same wall thickness as narrower rims. No extra metal is added except that needed for the extra width or height. I’ve done calculations based on the profile and the increased volume of of wider or taller rims and all of the extra metal is accounted for by the change in dimension. A “stronger” rim to me would mean one that has more metal to provide that strength.
Additionally, if you change the metal of the rim from aluminum to steel, the steel rim is significantly stronger and stiffer than an equivalent aluminum rim. It would resist the decrease in tension far better than an aluminum rim will but even the significant increase in strength doesn’t provide any protection against spoke breakage. Spokes still break on steel wheels.
Hjertberg has another, far nerdier,
article on spokes in which he posits that the increases in wheel strength are due to better metallurgy of the spokes.
Throughout our spoke making careers, the more we tested and watched empirical outcomes, the more we listened to metallurgists, the more it seemed that wire quality trumped all other factors. This is not a scientific observation since the number of variables is so high a reliable deduction process dwarfs my means. Still, we regularly saw outstanding outcomes when the wire was flaw-free. The worst hub, rim, tension, and load situations were easily handled with flaw-free wire. It is more than the absolute mechanical properties of the wire. It's processing success, making spokes not imbedded with fatigue catalyzing flaws in their microstructure.
The ability of low spoke count wheels to better withstand the rigors of riding has less to do with the rim than the far better spokes we have available today. I have no problem doing off-road bikepacking trips on some of the lightest, (presumably) weakest rims around…395g Mavic XC717 or 422g Velocity Aeroheats. But I pair them to DT Apline III or Pillar triple butted spokes. I went from regular spoke breakage pre-Alpine III use to no spoke breakage post Alpine III use. I haven’t changed how I build.