Rapid Wear on Cassette
 

The cassette that came with my Trek 1400 lasted thirteen years. The
replacement put on in July '04 lasted only four months, even though I
was riding only 60 miles a week! In particular, some of the teeth on
the smallest cog had been worn so that they were pointed rather than
square. This caused the chain to slip when heavy pressure was put on
the pedals.

How is it possible that the new cassette got worn down so quickly?
Am I doing something that accelerates the wearing down of the
smallest cog? For example, if I shift abruptly from a cog several
sizes larger to the smallest cog, there is a sort of crashing sound.
Is this what is causing the rapid wearing down of the smallest cog?

When you replaced the cassette did you replace the chain too?

A new bicycle chain has a 1/2 inch pitch so 24 links will be exactly 12 inches. As the chain wears, it appears to stretch. The same 24 links may extend to 12 1/8 inches or even more. When it does that, it wears the cassette teeth to match.

I generally replace my chains when 24 links measure 12 1/16 to 12 1/8 inches. I don't routinely replace my cassette when I replace my chain. Whenever I replace my cassette, however, I always make sure that it has a fresh new chain to start out with.

Yes, the chain was changed at the same time as the cassette.

I forgot to mention that when the first replacement cassette and chain were put on, I didn't grease the chain. Might that have something to do with the rapid wear of that cassette?

perhaps the rings are shot too?

Sram claims their chain gunk is a lube,with others it's more of a preservative.It's smart to lube it anyway,but not doing so isn't likely to have caused what you describe.

How often you do use your high-gear cog? You should use it only with the large chainring, and only for cruising at speed, particularly if it has only 11 or 12 teeth.

i also have worn out my cassette and chainwheel. seems my factory installed chain
was too long. checked with the locale bike shop, got new chain wheels,cassette, and chain and been over 2000 miles no probem.

Sure sounds goofy to me. That is extraordinary cassette wear. I can't think of what might have caused it. If you ran your chain with no lube at all, I'd think that the squeeking would drive you crazy before it would wear out your cassette in that short of a time.

You didn't mention the quality of the cassettes & chains you're using. In my experience, nine- & ten-speed drivetrains (Chains, cassettes, especially with 11-tooth small cogs, and chainrings) do wear quickly, so the two schools of thought seem to be either use cheap components and change them a couple of times a year or use more expensive stuff and try to get a season out of the drivetrain. Of course miles in the saddle, riding conditions, chain lube type and use, and drivetrain cleanliness are also important considerations. Here's more bad news, your right (Rear) shifter probably isn't too far behind the other components in wearing out.

It is maddening and expensive to maintain the precision required to realize optimum performance from modern drivetrains, but if you've been cycling for 25 - 30 years*, you know it's worth it.

*The "good old days" of thick 5 & 6 speed freewheel/cassette cogs (with relatively large 1st cogs), fat chains, larger chainrings, and friction shifters.

Sounds like you mash large gears and cross chain. Use your lower gears and spin more.