The plan was to swap the cassette and chain on my touring bike. Then events took over...
Ordered chain and cassette through work; they arrived last week, so I rode in on Saturday, swearing occasionally at slipping gear.
Drop wheel. Notice tyre is very worn. Swap tyre. Swap tube as well.
Swap cassette and chain. Realise chain wheel is filthy. We have a cleaning station at work so I could clean it. Laziness fights conscience for a few minutes, conscience wins. Remove chain wheel, dismantle and clean.
Notice brake blocks. My goodness but they're worn. Swap brake blocks on the basis the bike is in the stand anyway. Remember the headset is a bit loose so tighten that, after ten minute search for spanners.
Rebuild transmission, test. Gears playing up. Swap cable and sleeve.
No change. Remove mech, check dropper, find a slight bend, so I correct this. Gears still playing up. From experience this happens when the mech gets worn internally. I'd been keeping an STX mech for this eventuality; swap mech. New mech is even worse.
Fortunately I organised the used parts bin last year, and it pays off now. Find a pristine STX shifter I hadn't noticed before. Fit to bike, check gears. Much rejoicing: gears work.
Ride home. Nothing goes wrong; gears go, brakes stop, all good...