An Entropic Milestone

I was riding to work, waiting at a traffic light. Due to the geometry of that intersection, it is safest for me to declare myself in the actual traffic lane rather than sit meekly to the side where cars are willing to brush me aside to pass. Fifty feet after the intersection, there is plenty of space for me to move over. All I have to do is move out smartly and keep with the flow for fifty feet.

On a bike, it’s surprisingly easy to do just that. Watch the light, and when it changes stand up on the pedals, pull up on the handlebars to add arm strength to the power being delivered to the crank, and you as a cyclist can be the fastest vehicle of the cluster to reach fifteen mph. Past fifteen, cars have every advantage, but by then you’re through the danger zone, the motorists behind you appreciate your effort, and everyone parts friends.

Except on this particular ride, at this particular intersection, that’s not quite what happened. The light changed, I stood on my pedals with my skinny (but, I hasten to add, deceptively strong) legs, and began to pull through the intersection. Then… SKPOW! SCHWANG! My chain jumped right off the sprocket! (Not sure if it was the front or rear sprocket; I was too busy trying to not be killed.)

After a half-turn of the crank the chain caught again and the driver behind me did a good job not killing me. But I was a bit rattled.

A mile later, the chain jumped again. WTF?

One advantage of working at a big-ass company: There are company discussion groups about just about everything. I joined the bike-commute group (novices welcome) and asked what might be going on. I mentioned that my bike only had 3600 miles on it.

First came a response from someone asking for more details about my bike. Shit, I had meant to put in my first question, but spaced it.

How about this for a detail? My bike is a 30-speed. Thirty. Three gears in front (excuse me, ‘chain rings’), and ten in back. When I was a kid, there were two kinds of bicycles: bikes and ten-speeds. That was the entire taxonomy of the two-wheel world. My bike was a purple Scwhinn with a banana seat. It was awesome. One by one, however, my friends graduated to ten-speeds, and eventually I did too. Ten-speeds were the bosses of bikes.

Then there was the Schwinn Stingray 3-speed, with the big ol’ shifter lever. We all grew up knowing a guy from the next street over who had one of those. It was a bike, but it was the king of bikes.

Anyway, forty years later, once I revealed that I was riding a bike with a derailleur (or derailer for the less-pompous crowd), it was generally agreed that 3600 miles was more than I should have expected to get out of a chain, and that I was probably damaging my gears with every stroke of the pedals.

You see, the chain is a series of links with rollers that the sprockets mesh with. The rollers turn on the pins that connect the links of the chain. When the spacing of the teeth on the sprockets and the spacing of the links in the chain is exactly the same, all is happiness and joy, as the power delivered by my skinny-but-deceptively-strong legs is shared by every tooth on the sprocket that is in contact with the chain.

But as the chain turns, mile after mile, the pins that connect the links in the chain get worn down, which increases the spacing between links. Only a tiny bit, but that’s all it takes. Now at any given moment all the force of the pedaling is borne by a single tooth of the sprocket against a single roller in the chain, because the next roller in the chain is just a little to far from its corresponding gear tooth. Push too hard, and that one roller-tooth interface just can’t hold up. SPKOW! Even in normal pedaling, all the force from my muscles is being transferred through a single tooth of the gear, which can wear down the gears really quickly.

One more aside to acknowledge what you all are thinking: Yes, I did write this entire episode to brag about wearing out the chain on my bicycle. You know why? Because I wore out the freakin’ chain on my bicycle, that’s why.

Now I’m shopping for a new chain, and will be regularly. Unfortunately, there are a lot of options. They all are the quietest chains; they all shift the best. There’s one choice that costs twice the average cost of the other candidates, but claims to last longer (Diamond-like coating, whatever that means). Does it last twice as long? Pretty much impossible to measure.

I feel like I’m leveling up in the bike world. I’m a guy who wears out chains. I’m a guy who wears out tires. I’m a guy who knows what ‘chain ring’ means (it’s the gear in front). I’m the guy who flexes his calves in the mirror when no one is looking. I’m a bicyclist.


2 thoughts on “An Entropic Milestone

  1. I remember when I learned this lesson about my bike, in pretty much exactly the same way you did.
    The next two things I learned (perhaps your bike shop has already informed you):
    1) the other contact points of the drive train (the teeth of the front rings and back cassette) also wear down. They begin to resemble shark teeth, or shark fins. This wear is exacerbated when the chain wears as you describe. The chain is the weakest, and cheapest, link in the drive train. Replace it first.
    2) mechanics at my LBS (local bike store) can get me to smile proudly and gladly pay any amount they request with their oft-used comment, “of course the part wore out: you ride the shit out of your bike!”

    • Keith, your comment is prophetic. I just replaced my middle chain ring, after a rather exhaustive search for suitable part numbers.

      There are some chains that claim to last much longer (and they cost much more). Do you have any empirical data on whether they are worth the money? I have started a maintenance log for my bike, including a chain wear table. But for my riding, I don’t see the value of fancy chains unless they go farther.

      I think my LBS folks are still surprised that a gray-bearded pony-tailed old man is wearing stuff out. I’ve set a goal for myself to get 5000 miles on my bike by its first birthday, though at this point that’s going to be a real stretch. But that’s what goals are for, no?

      Next year 5000 miles will be routine.

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