The chain is, more likely than not, around the cassette. If you’re struggling to remove it, shift the front gear into the smallest ring. Find where the chain threads through two small wheels on the derailleur arm (the shifting mechanism on your back wheel), and push to put slack in the chain.
Skipped or slipping chain while riding. Issues shifting (Note: Check that your derailleurs are properly adjusted before changing the cassette) Visibly worn teeth (points are lower are rounder on some gears than others). Cracked, broken, or warped gears.
Some older lock-rings don’t have attached skewers. They are meant to replace the bolts on your own skewer, then used like normal. Unscrew the normal ends and put the lockring removal tool on your old skewer to use.
To loosen the bolt later you will need to turn the lockring counter-clockwise, so the chain whip will pull the the cassette clockwise – this is the opposing pressure to keep everything steady. Alternatively, use a length of chain instead.
Make sure the tool is firmly jammed in the cassette. This is easily recognizable by the 12-tooth lock nut on the cassette.
All this takes off is the lock ring, the small, usually silver piece that prevents the cassette from moving. Set the lock ring aside in a careful place – you definitely do not want to lose these!
Some teeth may slide off alone, and some may be pinned together. You may need to use a thin object to lightly pry a few gears off.
It’s tricky to mix and match gears, so it’s best not to try unless you’re experienced. Additionally, compatibility between gears and cassettes can vary. For example, a SRAM cassette may be compatible with a Shimano freehub body, but the new SRAM XD driver series isn’t compatible with any older model cassettes. Similarly, Campagnolo freehub bodies are only compatible with Campagnolo cassettes. If you’re in doubt about which one to use, consult your local bike shop. Note that changing gear ratios could require a longer or shorter chain to fit on new sized sprockets. The replacement cassette should have the same number of gears. For example, replace a 10-speed cassette with a 10-speed cassette instead of a 9- or 11-speed cassette.
You may need to add some gears one at a time. If they are separated, note any spacers (small, plastic rings) in between them when you buy the cassette. These must go on in order.
Hand tighten the bolt as much as possible, then use the wrench to just tighten it a hair more so it doesn’t move. You’ll likely hear a grinding sound while you do this, which will sound like popcorn. You’ll know the bolt is tight enough when you only hear 1 or 2 pops. The gears should all move together – there should be no play or wobble in any of the sprockets.
Always put the bike chain back near the gear the bike is in so that it doesn’t clank violently when you start pedaling. If confused, shift the bike all the way to one side of the gears and put the chain on the furthest two rings on that side.
