November 5, 2026

Goal today: swap the chain and cassette on my commuter before the weekend, because the drivetrain had been making a sound I can only describe as a bag of gravel rolling downhill.

I'd been measuring the chain with the Park CC-3.2 every few weeks. It had sat at the .75 mark for about a month — that's the point I try not to pass on a 10-speed Shimano system, since you risk pulling the cassette life down with it. I waited roughly two weeks too long, as it turned out.

1. Removed the chain with master link pliers. KMC link came apart cleanly first try, which is worth noting because it usually doesn't.
2. Pulled the rear wheel, clamped it in the truing stand while I had it out. Still within 0.5mm lateral, left it alone.
3. Removed the 11-34 Shimano HG cassette with the lockring tool and a 24mm wrench. Third cog from the smallest — the 14T — had visibly hooked teeth. That's on me: a chain measurement I skimped on two months back probably would have caught this.
4. Installed a new Shimano 105 cassette (11-34, 10-speed), torqued the lockring to 40 Nm, confirmed it seated flat.
5. Threaded a new KMC X10 chain, sized it, joined with a fresh master link.

The failure came at step 5. I tried to use a chain guide as a third hand to hold the chain end while threading — bent a tooth on the 17T cog. No excuse, I've done this long enough to know improvised tools create new problems. The 17T was borderline worn anyway; I had a matching spare in the parts bin and swapped it in. Chain ran quiet after that.

Next time I'd use a zip tie to hold the chain end. Five cents of plastic, zero bent cogs.

#bikemechanic #drivetrain #workshop #weekendwrench