Originally Posted by
KerryIrons
Before you do that (you might not even be able to find that cog) ride it for a couple 100 miles. The new chain might bed in and eliminate the skipping. But the standard way to determine whether you need a new cassette is when a new chain skips.
Actually, the Zizzo people gave me a 11T cog to replace it. I was just going to wait until the chain was at .75 to replace it and the chain but your suggestion seem like a possible solution.