Monday, October 25, 2021

What if your wheel collapsed?

 Back around 1980, a once-promising racer in the Maryland scene supposedly had lost a lot of his nerve when his low spoke count front wheel folded up in a sprint, sending him down from 30 to zero in the length of his own body. For you metric users, that's 48 to zero in less than two meters. When the front wheel disappears, the glide path is pretty abrupt.

Back then, low spoke count could mean 28, or maybe 24, and lightweight spokes were called "piano wires." I wasn't around before this rider had that crash, so I never knew him at his best. He was still plenty strong and skillful, but pretty good is not good enough for national-level competition. In a strong district, it isn't even good enough for regional prominence. You have to be willing to ride to die. On top of that, you need the genetics and the training to have the motor just to stay with a field of top riders. Anything that makes you the least bit hesitant is going to cripple you.

Nasty crashes can happen to anyone, for a wide variety of reasons. Equipment failure is not limited to high performance equipment built to thin margins of safety. On the plus side, incipient equipment failures can be detected by inspecting a bike regularly. Sometimes these failures make themselves obvious, as with previous cases of spontaneous spoke or nipple failure I've reported here.

The worst case scenario is that someone hops on their recreational bike that's been sitting in storage and pedals away without noticing that a couple of spokes have failed, and manages to get up to a moderate speed -- down a hill for instance -- before the wheel folds up. Of the two, a rear wheel is only slightly preferable, since it's not going to lead directly to a face plant. You'll still hit the ground abruptly and hard. Fortunately, most of the time, other issues will prompt a person to bring their bike in for a check up before they go out, or will stop them early in their shakedown cruise, as rusted chain links or some other drive train interference make the bike too hard to ride.

One case of spoke failure this summer showed up on a Schwinn recreational bike with an internally-geared hub. It had a couple of broken spokes. This can happen in storage if something gets shoved into the bike, or it can happen when several bikes are stacked on a rack on a car, or in a crowded parking situation, or a crash.

Closer examination revealed that the spokes had simply come apart. Every spoke in the wheel was banded with rings of rust that had eaten most of the way through them, except for the ones that had already disintegrated.


If you look closely, you can see a piece of spoke at an angle, impersonating a normal bend. You could crumble these spokes in your hand, into little fragments. They had no tensile strength at all.

With the current problems getting parts, my only choice was to respoke the wheel with a different cross pattern to match the lengths of spokes available. It went from three-cross to four-cross, which will just provide a cushier ride. I built my first touring wheels four-cross because it was supposed to be better for long hauls at moderate speeds, with a load. It was all right. I've had to depart from basic three-cross on other occasions as well. It's all legit. I generally don't go below three-cross except by customer request.

Stripped down, the hub felt like something you could use to train for the shot put. It weighs 4 1/2 pounds.

My wife, who competed in the shot put as part of her track and field career in school, informed me that the women's shot is almost nine pounds, and the men's is 16. But we could have a "hub put" category added to the Huffy Toss if we ever have a bike shop field day. Regulation weight could be whatever we say. This hub was still a hefty handful. Holding it up to load the spokes, my arm started to get pumped.

Within a day or two, another wheel job came in and I reflexively wrote it up for respoking, even though we could have replaced the wheel with a complete pre-built wheel. This is another example of how cheap labor has led to replacing rather than rebuilding something because parts and labor cost more than a new unit of low to modest quality.  In the wheel department, this is nothing new. My friend in Florida worked as a contract wheel builder in the 1970s, paid by the piece. I don't know if any US supplier uses American workers for that sort of thing anymore. She also wasn't trying to support herself on the income. It was supplemental in a variety of gig jobs, in a duo with her talented and enterprising husband before he finished his aircraft mechanic certifications.

The wheel I built was better than mass-produced, and it saved a complete wheel for someone who might need it more. It's good to stay in practice. I'd observed early in the season that people don't have much use for wheel builders anymore, and promptly started getting wheel repairs and complete builds.

A conventional build doesn't take too long, which might make it seem cheap and easy, but you do need to know how to make it efficient as well as quick. Proper tensioning takes most of the building and truing time. That's the part that takes experience. It's easy to get into trouble by rushing the tensioning phase. 

Novice builders will make two common mistakes: go for lateral trueness before roundness, and stop with too little tension once the wheel is as close to perfectly true as they can get it. After they've had a few of their creations develop the wobblies because of inadequate tension, they might move on to the intermediate mistake of too much tension. You can buy a tensiometer to check whether tension is sufficient and even, but after a while you will develop a feel for it by squeezing and by how the spoke wrench feels when you turn it. Check your calibration with the tensiometer occasionally.

A big part of the cost of custom wheel building is that we only get parts at wholesale, whereas most mass-production builders get a price that is at least one tier lower, and probably even better than that. They can take a margin on parts and labor that compensates them well, and still undercut us for the same parts on the same build pattern. When we have unrestricted access to supplies, we will often spec a pre-built wheel that matches what we would have done anyway. Reputable production suppliers have become pretty good at spitting out consistently acceptable wheels. And if you want something tweaky and modern, super light and fashionable, you will have to buy complete wheels. If you want something a little more tailored, based on rim width or a preferred brand, then you have to find someone to put that together for you.

2 comments:

Rob in VA said...

I assume the spokes that exhibited rust bands on the Schwinn wheel were supposedly stainless steel...have you seen this type of deterioration very often? Do you suspect it resulted from inferior metallurgy?

cafiend said...

have not seen it often, but I’ve seen versions of it, usually on black spokes. The black coating seems to give rust a place to start, and contains the damage, concentrating it more rapidly in the interior of the spoke. Stainless steel refers to a range of formulations, some more stainless than others. I’ve seen rusty spokes on cheap bikes, but this was the first time I’d seen them utterly crumbling.