You know that glorious feeling the first evening of Daylight Savings Time when you head home from the office on your bike? If you’re lucky there’s a little sun on your face and the temperature is well above freezing. That’s your cue to replace your chain (and your smoke detector batteries).
On the Xootr Swift Folder bike, we recommend the KMC Z72. It’s totally bulletproof, easy to install, and very inexpensive. Note that you do need to match the chain type with the number of cogs in your rear cassette. The Swift uses an 8-speed cassette, so the Z72 is the right chain. KMC, SRAM, Shimano and others have different chains for cassettes of different types. Incidentally, one of the reasons we use an 8-speed cassette is that you can use an inexpensive and utterly standard chain. If you are using a more exotic cassette, you’ll probably want to stick to the brand of chain that matches the cassette (e.g., Shimano with Shimano and SRAM with SRAM).
Here’s why you should replace your bike chain every year if you commute by bike.
- If you ride in all weather and are not obsessive about chain maintenance, then the little pivot points on your chain will have worn significantly in a year. People sometimes say a chain stretches, but chains don’t stretch. Rather, what happens is the little pins get grit in them and wear a little bit, so that there is maybe an extra one thousandth of an inch of clearance between the little pin and the hole it fits in. That extra thousandth becomes an extra tenth of an inch over the length of the chain.
- When the spacing between links on your chain gets a tiny bit greater, then the spacing on your cassette teeth won’t be quite right. Think about it, if the cassette is designed for a spacing of 0.500 inches and because of wear, the spacing is actually 0.501, the chain is not going to quite match up with the teeth, especially as it wraps around the cassette. What has to happen geometrically is the chain has to ride up a little higher on the teeth (to effectively increase the diameter of the cog). Your cassette and your chain will wear together with little bits of the gear teeth eroding away as the chain rides higher on the cog. If you let this co-wear happen for a few years, a new chain will not fit on an old cassette — the chain will skip like crazy. Instead you’ll have to replace both together. On the other hand, if you replace your chain every year, you’ll probably be able to make a cassette last for ten or more years.
- One of the worst mechanical problems you can have on your bike commute is a broken chain. Unless you are the kind who carries a chain tool and an extra connector link, you’re pretty much stuck walking. (It’s also a very greasy repair.) It’s pretty near impossible to break a newish Z72 chain. I’ve never known it to happen. So, replace your chain every year, and you will probably never break a chain.
How do you replace a bike chain?
It’s really easy with an 8-speed chain like the Z72, because it comes with a connector link. Here are the steps.
- Use a chain tool to push out a pin to “break” the chain. Incidentally, get a good chain tool. Life is too short to deal with a lousy chain tool. I like the Park CT-3 for a shop tool and the CT-5 for a tool you can also carry with you.
- Lay the old chain down on the floor.
- Line up the new chain with the old chain, and remove the extra links from the new chain so that it has one fewer link than the old chain (because the connector link will add one more link back to the length). You should end up with both ends of the new chain being “inner” links (the thinner ones), because the connector link is an “outer” link.
- Thread your chain around the rear cassette and through the derailleur cage, being sure everything is riding on the tensioning cogs properly (reference the photo or a bike with a chain through the derailleur to be sure you got it right).
- Run the chain towards the front of the bike around the crank spindle and through a front derailleur cage if you have one. Don’t actually place it on the front chain ring though, as this makes it harder to pull the two ends of the chain together to connect them.
- Use the connector link that comes with your chain to connect the two ends of the chain. Pull the chain to connect the two halves of the connector link, but don’t worry about actually “seating” the link with your hands. The first time you pedal the bike you’ll hear a “click” as the link settles in final position. Now install the chain onto the front chainring and you’re good to go.
If it’s Daylight Savings, it’s time to replace your chain.