Tuesday, August 6, 2013

Working On The Chain Gang

I promised that I wouldn't review a chain, and I'm keeping that promise -- there's a lower limit of "boring" that even I won't cross. But with a chain on the way out and another one on the way in, I thought it might be a nice time to review the basics of chain replacement.

First, a pet peeve from years in ye olde bike shoppe. Chains do not stretch. They get longer, yes, but that increase in length is not "stretch" caused by the massive power output of your trunk-like thighs -- unless you were sent here from Krypton by your father Jor-El. So if that isn't "stretch", how is it getting longer? Remember that each connection between those hundred-and-some links is a mechanical one, two metal surfaces rotating against each other. Unless you have a full chaincase, those mechanical connections are exposed to dirt, sand, grit, sweat, rain, and any number of other gross things. Grit plus moisture equals grinding paste, wearing away the tiniest amount of metal with each rotation. On one link, it doesn't make much difference, but over 100-plus links and some time, it adds up.

So now you have a chain that has just a little too much space between its pins. Run that over your cogs and chainrings long enough (adding some more of that gritty paste) and pretty soon, those parts start to wear to match the new spacing of the chain. The worst part? You might not notice. Since they're all wearing together, those parts can continue to work in harmony long after they've passed their expiration date. Only when you think, "I'm too lazy to clean that chain, so I'll just replace it," does the awful truth reveal itself. Your new chain has factory-spec spacing between the pins, but your cogs and chainrings are expecting their old buddy, Worn-Out Chain. Your drivetrain's now on a ride to Skip City, and your bike shop just made some money on your new cassette and chainrings to go with that new chain. That was, hands-down, my LEAST favorite conversation to have with a customer back when I was a shop wrench -- it always sounded like one of those "bad mechanic" horror stories: "So I buy this $15 chain, and the guy tries to tell me it won't work without buying $75 worth of new parts! Can you believe it?"

Fear not, though! All these woes are preventable, and they shouldn't cost you one cent (assuming you aren't already in the express lane headed toward Skip City). How? Grab a ruler that you don't mind getting dirty. Measure 12 links of your chain under a little tension. If the pin on that 12th link lands smack on the inch line, your chain is new, so why are you measuring it? If it's past the inch but not to the 1/16th mark, you're still okay. At an inch and 1/16th, get a new chain, but the rest of your drivetrain should still be fine. Out around an inch and 1/8th? Uh, sorry dude. There's a great coffee shop in Skip City, though. 

(Note that, like most things bicycle, the late, great Sheldon Brown does a better job explaining much of this -- with great photos, no less -- in his article on chain maintenance. I learned it in the trenches, but if you don't have a few years to kill and a penchant for greasy aprons, you could do a lot worse than to study the Gospel According to Sheldon.)

If you don't have a ruler, hate fractions, or just feel an uncontrollable urge to own more bike tools, there are lots of nifty gadgets to accomplish the same thing. I use the basic Park model for its stupid-simplicity: If only one side fits, I order a new chain. If both sides fit, I curse my inability to take my own advice. The old shop model I used in the 90s was even stupid-simpler: Stick it on the chain and turn a dial. If you see green, all's good. If you see red, you're screwed (the new fancy model expects mechanics to read numbers, which not all of us can do).

Final chain rant, then I hope I've sufficiently cured your insomnia: Whatever brand of chain you like, and however many speeds you spin, I can't say enough nice things about modern master links. I've dealt with SRAM, KMC, and Wipperman, and I like 'em all. I still carry a chain tool as a security blanket (you can't shorten a chain to make an emergency singlespeed without one), but (knock wood) I can't remember the last time I used it. A pox on Shimano and their stupid one-use-only, can't-be-installed-without-a-tool pins! I stopped using their chains specifically because of those things, and if I had to use one again as part of some lucrative sponsorship deal for fat commuters, I'd conveniently "lose" the pin and rejoin the chain with someone else's master link.

Everyone paranoid and looking for a ruler now? Then my work here is done.

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