The gist of the problem is that you have to turn the lockring counter-clockwise relative to the cassette to remove it. When you turn the lockring counter-clockwise it pulls the cassette by the teeth that were locked in place when you tightened it during installation, and the cassette freewheels in this direction. So you need to immobilize the cassette against the wheel. A chain whip does this with two separate pieces of chain and a handle for leverage. We'll do it with one piece of chain attached to the cassette in opposite directions, looped around so it can be braced against the wheel by a screwdriver. A similar approach involves attaching the chain to the rim/tire with zip ties or string; my zip ties were all too wide, so I tried with string and broke the string. Some people say they can get their lockrings off just by grabbing the cassette by hand with a rag for protection. My lockrings always get on way too tight for anything like that — even with a chain whip it's always a lot of effort to remove them!
- The cassette lockring tool
- A wrench that fits your cassette lockring tool
- A reasonably sturdy screwdriver
- An old chain, full-length (broken and off the bike)
- The wheel should have an inflated tire on it!
- Do all the prep you'd do if you were using a chain whip: take the wheel off the bike, remove the quick-release skewer, insert the lockring tool according to its instructions (some have a dummy skewer attached, while others have a hole in the middle, and you stick your skewer through it and secure it with the screws).
- Put the chain around the top half of the second-largest cog, with almost all of the excess hanging off to the right.
- Extend the excess chain on the right out past the edge of the tire.
- Loop the chain, to the left, back to and around the cassette, one or two cogs smaller than the first. The loop should extend a bit past the edge of the tire, enough to stick the screwdriver through. At this point, with the chain around cogs in opposite directions, turning the cassette counter-clockwise (in the freewheeling direction) shortens the loop.
- Stick the screwdriver in the loop, with the chain loop around the handle and the shaft against the tire. This prevents the loop from being shortened, so the cassette cannot turn relative to the wheel.
- Stand the whole thing up between your legs, with the screwdriver against the ground. Brace the screwdriver in place with your feet on either side of the wheel.
- Turn the lockring tool counter-clockwise with the wrench. This should pull the screwdriver tight against the wheel, allowing you to put a lot of force into the wrench. Eventually the lockring teeth should break free and the ring should loosen.
And here is the world's worst diagram, since I didn't feel like staging a photo while I was working on my bike earlier: