The cassette is the stack of sprockets on the rear wheel that the chain runs over. It collects dust, grit, mud and old lube that slowly turns into a black abrasive paste, making shifting worse and wearing out sprockets and chain faster.
You can wipe the cassette on the bike, but once or twice a season it is worth removing it for a full clean. That also avoids contaminating the brake pads.
What you will need
Important: Remove the wheel and clean the cassette well away from brake discs and pads: degreaser or lubricant overspray on them seriously reduces braking. You can cover the disc with a cloth.
Step 1
Remove the rear wheel
Shift onto the small chainring and the smallest rear sprocket. Release rim brakes; with discs, do not squeeze the lever while the wheel is out.
Open the quick release or thru-axle, or undo the nuts, pull the derailleur back and lift the wheel out of the chain.
Step 2
Take off the cassette
Lay the wheel on a bench and fit the tool into the lockring splines. Wrap the chain whip round a large sprocket to stop the cassette turning.
Holding the whip, turn the tool anticlockwise with the spanner. After half a turn the lockring will give; unscrew it by hand and slide the cassette off the freehub.
Step 3
Keep the sprockets in order
If the cassette comes apart into individual sprockets and spacers, thread a cable tie through them so you cannot mix up the order or the orientation when refitting.
Step 4
Wash the sprockets
Place the cassette in the tub, wet it and spray each sprocket generously with WD-40 Multi-Use. Leave it a few minutes to dissolve old grease, then scrub between the teeth with the brush and paintbrush.
For a very dirty cassette after winter riding, use WD-40 Bike Degreaser. Rinse with water and dry thoroughly.
Step 5
Clean and grease the freehub
Wipe the freehub body clean and check the splines for burrs. Apply a thin film of WD-40 Specialist White Lithium Grease to the splines to prevent corrosion and make the next removal easier.
Step 6
Reassemble and refit the wheel
Find the wider spline on the freehub and the sprockets and line them up. Slide the sprockets on in order with their spacers, then cut the cable tie.
Thread the lockring on by hand and tighten with the tool, ideally to about 40 Nm with a torque wrench. Refit the wheel, check brakes and shifting, and lube the clean chain with WD-40 Bike chain lube.
Tip: A clean cassette is quickly ruined by a dirty chain, so do both together: while the cassette soaks, clean the chain and chainrings, and lube only the chain, never the cassette.
What next
Deep-clean the cassette once a season, more often if you ride in mud or through winter. In between, wipe the sprockets with a cloth dampened with WD-40 Multi-Use and lube the chain after every wet ride.
These uses come from the experience of WD-40 users in many countries. Always follow the instructions and warnings on the product label.
More guides in «How to use».