Cassette Replacement?
 

Begining of season, I checked, and chain was barely showing wear. 2-3 months later and oops! at 1/16th and rollers are kinda loose. Need to step up my chain lubrication, clearly, as I doubt I have much more than 1kmiles on this chain. Anyhow, since this is the second chain I have worn out on this bike, I looked at the cassette, figuring I'd have more wear on the hill climbing gears--wrong. The gears I run in the flats may be worse: on the edge of the tooth where the roller would ride while pedaling hard, on the edge of it, I can easily catch a fingernail. As if the tooth was being hammered flat by the chain roller. I'm guessing, time for replacement?

Bike is a Trek Pilot 1.2, 9 speed setup, SRAM PC-951 chain (first chain was Shimano whatever). Cassette is whatever 12-25 that came with the bike. I've thought about stepping down to a 12-23 (not sure if an 11 would fit, nor my actual need for an 11) or maybe even 12-21, so it'd be a great time to try that idea out; but figured I'd ask before I assumed my cassette to be on its way out.

Thanks.

There are different schools of thought here. Some would tell you to replace the cassette in the condition you describe. I'm of the replace no cassette before its time school. IMO the only reliable way if knowing if it's time is to install the new chain and see how it goes. If the chain runs OK, then you're good to go.

If it skips under load, the cassette is toast. As the cassette nears the end, a new chain will run rough (you feel it in the pedals especially under moderate load. Here you can make a jusdgement call as to how much more you want to squeeze out of it. For example, on my commuter I'll put up with anything short of slipping, but on my road bike, 100miles pedaling with a rough train is unacceptable and I'd replace it.

BTW- you are definitely getting sub pat performance out of your chain lube, or more likely how you're applying it. Unless you're an animal riding in the Alps, you should do vastly better on a chain, something like 3-5,000 miles service life, with 10-20,000+ miles service life on a cassette.

Yeah, it's called "apply lube when I think of it", and I never actually clean the chain. To be fair, I do have to stand to climb a number of hills, and I don't shy away from bombing down dirt roads. The latter wouldn't be a problem if I bothered to clean, the former will always be hard on the drivetrain. I should just get in the habit of oiling it once/week and cleaning once/week or once/month--I might do better on a fixed time schedule. Personally, I'm just glad that I'm riding enough to wear stuff out--means i need to pay more attention, but also means I'm getting the miles in.

I might just buy another cassette, but either 12-23 or 12-21, as I've been wanting to experiment with that. Won't hurt to play a/b, and I'll have a working cassette if the current one really is toast.

Thanks!