So I'm wondering something about replacing your chain. My LBS will NOT replace the chain without also putting in a new rear cassette. Is this a real thing? Can you put a new chain on and still use the cassette you got? It kind of makes it a little expensive if you need a new chain.
Your bike shop is probably covering their butt. You don't need to replace your cassette when putting on a new chain. The exception would be if that old chain was used beyond it's useful life and completely flogged before replacement. If your chain has been used for many thousands of miles and or had iffy maintenance, your cassette will most likely need replacement. If the chain is real bad, it will cook your chainring(s) as well
Bike shops are so busy these days they'll hire anyone.
They have it backwards. If you replace your cassette you need to replace your chain (generally, unless the chain is also pretty new). A good cassette should last 3 or 4 good chains.
One possibility is if you have like 6k miles on a chain it probably damaged your cassette, but that noise would probably drive you insane first.
Measure your chain with a chain-checker tool, something like a Park cc-2, if chain measures 1.0 or more, a new chain will likely skip in your most used cassette cogs. —Sometimes it gets some better as the new chain runs-in.
Yeah, I had an LBS tell me that once. I said pass. If your chain is way, way worn - you probably should. Generally you'll see some wear on the teeth too. But if you are not seeing any problems shifting, and don't have the chain jump teeth with 1000 watts of acceleration - well if it ain't broke, don't' fix it.
I will say that these 1x bikes with super small cogs are gonna wear a lot faster than the standard 2x setup. If you are spending much time in a cog smaller than 14t, you are gonna get a lot of wear on the cassette. Certainly a cassette with a well used 10t cog is have to be replaced more often than the old school stuff.