In the event that you, gentle reader, have been having a difficult time getting to sleep, this article should do the trick. For the record, Pedal does not recommend dozing with a hot laptop in your lap. Ever.
The first two bikes brought into Pedal for service had chain stretch, and both owners were moderately surprised by the news.
Your chain is the wear item on your bicycle, and it’s an insidious piece of work because it’ll wreck other parts of your drivetrain if it isn’t replaced in a timely fashion. As such, it’s probably worth a few words.
Chains “stretch” due to wear at the intersection of their various parts. As wear occurs, the measured distance of each chain link increases — not because the actual side plates stretch, but because things get “loose” at the rivets.
Chains and the rest of the drivetrain (cassettes, cogs, chainwheels, etc.) are manufactured based on a standard length for a link of chain. As the chain wears and the links become effectively longer, the harmony between chain and cog deteriorates. And here’s the sneaky bit: the worn chain will slowly deform the teeth on the cogs, cassettes, chainwheels, etc. so that they match the chain. If the chain becomes quite worn, the drivetrain components will no longer mate with a new chain, and other parts must be replaced. This is the source of many a higher-than-expected repair bill and shocked customer.
How much stretch is too much? For modern 9- and 10-speed drivetrains, the rule of thumb is that a chain should be replaced when it achieves 0.75% stretch. If the chain is 1% stretched or greater, the cassette has also been deformed and should be replaced as well. A very stretched chain will even deform chain rings, the replacement of which can be a pretty expensive proposition. Bad news for Campy folk, your 11-speed chain should be replaced at 0.5% wear.
Since mechanical wear is the cause of chain stretch, one should strive to minimize the wear by keeping the chain clean and lubricated. It’s OK to hose off your chain if it’s gritty. Just dry and lube it after the wash. What to use for lube? Chain lube is cheap and lasts a long time. When you lube the chain, put the goop on the chain and — this is the important part that everybody misses — leave it alone for a while, a couple of hours, days, whatever. The lube needs a chance to work its way into the nooks and crannies that need the lube. Once the waiting period is over and before you ride, wipe off the excess. It does no good to sling that nasty lube all over your bike, and you don’t want grit to get all over your sticky chain and make things worse.
Quick recap: clean chain, dry, lube, pause, wipe off excess, ride.
How many miles can one expect from a chain? This is one of those terrific/awful questions with no pat answer. If you let your chain rust, it’ll be a goner very quickly. If you are something of a masher, your chain suffers. Grit in the drivetrain? Not good. I found an interesting piece of data, but it comes with a big caveat: it was compiled by a company that makes bicycle chains. Here it is
This data suggests that a 10-speed chain will last anywhere from 1000 to 3500 miles. Alas, that has been my experience. I’ll leave it as an exercise for the reader to take the supplied data and work on the dollars per mile for various chains.
Questions? Concerns? Bring your bike by the shop and we’ll measure your chain. Free Of Charge.