Video: What's the Deal with Chains? - The Explainer

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I get it, chains are about as interesting as yet another sponsorship farewell announcement by some rider saying goodbye to some company, neither of which you give a toss about. But they really do deserve better, given that they're probably one of the most important yet least cared for components on your bike, and even though the only time most of us think about them is when we're on the side of the trail trying to put one back together.

This week's Explainer is all about where chains came from and why we're using them. We'll also take a look at a few very strange and long-extinct chains, and address some common misconceptions.




A Brief History of the Bicycle Chain

So, where did they come from? Back when bicycles had massive front wheels that were driven directly by the cranks, along with comparatively tiny rear wheels, people kept falling off and hurting themselves because, well, these things were pretty sketchy. Eventually, someone in England made a bike with equal size wheels that meant riders didn't have to be perched way up high, but now they had to figure out a way to translate the action from people's legs to the bicycle's forward movement. Of course, there were some strange contraptions around this time, but an early version of the chain-drive won out, largely because you could easily adjust the gearing by swapping the cog or chainring for ones of a different size. This was all happening in the late 1870s, long before people had to think about derailleurs and gears, and chain design was far from being standardized.

The simplest of these had to be the bar-link chain that used a 1" pitch (the distance between each pin, and double what's used today) and looked like the chain a six-year-old might draw. Or me right now. There were no rollers or inner plates, making it incredibly inefficient, and it disappeared from bicycles in the early 1900s. There was also the skip-link chain that used side plates of alternating length to vary the distance between the pins, supposedly to help make it more efficient. It stuck around until the 1950s.




The strangest? That has to be the crazy-looking Simpson lever chain that's pictured above. Levers? Yup, it looked like a bunch of tiny triangles strung together, and its maker said that those provided the rider with extra leverage. It went away in the late 1890s, around the same time that American velodrome racing went from attracting crowds of 20,000 people to nearly going extinct.


The Modern Bicycle Chain

If you want to be technical about it, it's actually called a roller chain, and there are many different kinds out there being used on all sorts of machines. Today's bicycle roller chain sports a 1/2" pitch - the distance between each pin - regardless of how many cogs you might have. 6-speed? Yup, 1/2" pitch. 12-speed AXS or XTR drivetrain? Still a 1/2" pitch.


This means that the rollers spin on tiny shoulders that are stamped into the inner plates, whereas an older version might employ a bushing for this job. Last but not least, the pin runs through it all and hopefully keeps everything together despite all those squats and lunges you're doing.


Misconceptions

You're so strong that you broke your chain: That's a hard no. Your chain didn't break because you're really strong, even if you actually are. Wipperman, a European chain manufacturer, did a test of 10-speed chains back in 2007 and the results might be surprising to some: The tensile strength - the force required to simply pull a chain apart - ranged from 9,100N up to 10,800N. That's 2,045lb to over 2,400lbs, or approximately one Toyota Yaris hanging from a chain. That's a freakin' car. Also, the European ISO standard that every chain manufacturer has to meet is about 1,800lb.

So, why do chains break? The most common reason for a broken chain: Shifting while you’re putting down all those ponies you have, which can twist the chain or see the cog teeth pry an outer plate off of the pin. But sometimes it’s just bad luck, too. When that happens, it starts a chain reaction and the whole thing can twist apart.

Skinnier chains are weaker: Nope. Chains aren't getting weaker, either, despite being skinnier than ever. Testing points towards modern 12-speed chains being more reliable and stronger than ever, largely due to improving materials, manufacturing, and tolerances.




Belt or shaft drives make more sense: Not for anyone who wants to pedal their bike for any length of time. The problem is that you put out around single horsepower. Just one. So you can’t waste any of that, and belts and shafts are really, really inefficient for all sorts of science reasons. But the same science has chains being something like 95 to 98-percent efficient, which might not seem like a big deal if you have a full-face helmet hanging on the handlebar of your 35lb all-mountain bike that's years old, knee pads on, and just want to go do some jumps - I mean, who cares, right? A lot of people, because it matters.

Of course, belts and shafts don’t play nice with derailleurs, either, and chains can be taken apart easily for installation and removal. What about a gearbox then? We'll leave that topic for a future Explainer video.

Your chain is stretching: Nope, you aren't strong enough to stretch the plates, sorry. What’s actually happening is that you’re wearing material off the rollers, the tiny “bushing-less” shoulders they roll on, and even the pins. As all that wears, the distance between the rollers grows, effectively increasing the pitch from the ½” it’s supposed to be. Because the rollers are farther apart, the pitch is larger and doesn’t match the cog’s teeth, which means it can’t fully engage and will even slip off the cog’s teeth.

Alright, but then why does it measure longer when you compare it to a new chain? As the pins wear, the holes in the plates they're pressed through wear as well, thereby letting the chain "grow" in length.

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Previews Explainer episodes:
Episode #1 - What's the Deal with Linkage Forks?
Episode #2 - Carbon Fiber Leaf Springs

Filmed & Edited by Cole Nelson