Originally Posted by
Marcus_Ti
The other advantage of small-small is that because you are getting the longest-possible chain size, you can change to larger cassettes up to the rated capacity of your derailleur without needing a new chain.
For such a scenario to occur...I can only imagine it if you are not properly doing small-small (allowing FAR too much space between the chain and the RD arm in small-small)...or if you are using a cassette beyond the rated chain wrap of your RD.
Which is actually fairly common when swapping cassettes for a big hill ride if your bike is fitted with a short cage RD. Its still fine though if the chain is long enough because small-small isn't that useful