Originally Posted by
DaveSSS
I expect a cassette to last through at least three chains. The idea of swapping the cassette and chain at the same time is a LBS scam to increase sales. You can leave one chain in use for too long and find that one or more cogs skip when a second new chain is installed, but that is user error. Rather than toss chain when they are half worn to avoid chain skip, I take them off, but keep them for reuse. If you use 3-4 chains in a regular rotation, you'll never get chain skip and the cassette will last as long as all of those chains.
You make it sound like all the shops got together to hatch a diabolical plan to "scam" people out of their money regarding chain + cassette replacements. They don't. People who bring bikes in to be serviced, a very large majority of the time don't care or have the money to care about a involved chain rotation formula of dubious value. They just want their bike to work.
Does a 3/4 chain replacement strategy also mean that you get 3/4 cassettes out of them? Really the only thing your strategy does is attempt to recycle a chain that hasn't worn the cassette enough to have a new one skip - when you do put a new one on the wear doesn't stop. Eventually it will skip in all 3-4 chains you put on, and the rotation frequency has to increase towards the end of the cassette life. So you used 3/4 chains and their cost to do what exactly? Where's the advantage?
It's definitley not ease of maintenance or economy.