Changing rear cassette

[DebW]

Even with a short cage you can use the 13-29 cassette PROVIDED that you don't use the 50 chain ring in the front with 29 cog on the cassette.

But on rare occassions one may shift to the largest rear cog without remembering which front cog one is on. In that case, the chain would jam and it wouldn't be good. You may damage chain, derailleurs, cogs, or crash.

Need chain whip on a cassette I thought all you needed was the sprocket-wrench-thingy-magingy to loosen the lock ring that holds the cassette in place.

The cassette will freewheel in the direction you need to turn the lock-ring tool to remove the lock ring. A chain whip is required to keep the cassette from turning. To tighten the lock-ring, you don't need another tool.