Repair notes

Checking Chain Wear Before You Trash Your Cassette

I learned this lesson the expensive way: ignore your chain long enough and you'll be replacing your cassette too, maybe even your chainrings. Now I check chain wear every few weeks in my freezing garage, takes about two minutes, and it's saved me probably two hundred quid over the years. Here's how to actually do it and why it matters.

Why Chain Wear Actually Matters

Chains stretch as they wear, except they don't really stretch, the pins and rollers just wear down and create slop between links. This means the chain gets longer, and when it gets longer it starts grinding into your cassette teeth like a file. Those teeth are hardened steel but they'll still wear into shark fins if you run a stretched chain long enough. I did this once on my commuter and had to replace both the chain and cassette when I finally got around to it. The chain cost me fifteen quid, the cassette was fifty. Now I just check the chain regularly and replace it when it's worn, before it eats the expensive bits.

How to Measure It Properly

You can buy a chain checker tool for about eight quid and it's honestly worth it. The tool has two prongs, you stick it in the chain and it tells you if you're at 0.5% wear, 0.75% wear, or 1% wear. For most riding I replace at 0.75%, for my winter bike I sometimes push it to 1% because I'm replacing that cassette more often anyway from all the grit. If you don't want to buy a tool you can use a ruler, measure twelve full links pin to pin, should be exactly twelve inches on a new chain. If it's twelve and one-sixteenth you're past 0.75%, if it's twelve and one-eighth you're way overdue. The ruler method works fine but the tool is easier in a cold garage when your hands don't want to hold steady.

When to Check and When to Replace

I check every month or so during riding season, more often if I'm commuting daily or it's been wet. You're looking for that 0.75% mark on most bikes, maybe 0.5% if you're running an expensive eleven or twelve speed setup because those cassettes cost actual money and the narrower chains wear faster. Write down when you installed the chain if you can remember, helps you figure out how many miles you're getting. I get about two thousand miles on a chain on my road bike, maybe fifteen hundred on the winter bike with all the crud. When the checker says it's time, it's time. Don't try to squeeze another month out of it, you're just gambling with your cassette at that point.

The Cold Garage Reality Check

Look, I put this off all the time when it's January and the garage is four degrees and I just want to ride. But here's what I do now: I keep the chain checker hanging on a nail right next to where I store the bike, and I check it while the bike's still dirty before I even think about cleaning. Takes literally ninety seconds. If it's worn I order a new chain that night and swap it next ride, which is another ten minute job. The alternative is ignoring it until something starts skipping under power, then discovering you need a chain and cassette, then waiting for parts, then spending an hour in the cold garage doing a cassette swap which is way more annoying than a chain. Check it now, replace just the chain, ride happy. That's the whole thing.

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