What happened to my teeth?

[Onno]

That is, the teeth of my DA cassette. Drivetrain suddenly getting pretty noisy, skipping a bit. Replaced the chain, it just gets a little worse. I took the cassette off tonight and inspected it. Amazing how tiny the teeth on all but the smallest cogs have become. Little baby teeth. I guess 15,000 miles is a real limit. Just ordered a new one.

[531Aussie]

wow! 15,000 miles is a lot, in my opinion!! :)

You can't put a new chain on old cogs, as you've found out.

Your cogs are too far worn. Small, 'pointy' teeth are an indication of heavy wear

[Charles M]

does your chian now have little tiny rollers? :)

[avalonracing]

does your chian now have little tiny rollers? :)


It probably has enough lateral movement to work on its side!

[Kevan]

15k?! You got off lucky.

[Onno]

I've been good about keeping the chain clean, and replacing the chain regularly. I've had 5 or 6 chains (about 1 a year) over the lifespan of the cassette. I'd just got so stuck in the idea that replacing the chain makes everything silent and smooth that I forgot to think about the cassette. It worked and worked, and then didn't.

[Dave]

I've been good about keeping the chain clean, and replacing the chain regularly. I've had 5 or 6 chains (about 1 a year) over the lifespan of the cassette. I'd just got so stuck in the idea that replacing the chain makes everything silent and smooth that I forgot to think about the cassette. It worked and worked, and then didn't.

Cogs won't last forever, no matter how often you change the chain. If you really want to get 15,000 from a cassette, you should consider alternating the use of 3-4 chains, and not allow any chain to remain on the bike more than 2,000 miles before alternating. In that manner, you never install a brand new chain on cogs that are too worn to mate with it. Shimano chains elongate a lot faster than Campy chains, so frequent alternating is more important. With a Campy drivetrain, I alternate 3 chains at 2500 mile intervals and expect to get 15,000 from the three chains and one cassette. The third new chain goes on the cassette at the 5,000 miles point and shouldn't skip on any cog, unless you use only one an awful lot. After 7500 miles, you've got three half worn chains that can then be alternated at just about any frequency, but I'd recommend more frequently, like any time you have the chain off for cleaning.

I made the mistake of using chain elongation as a wear guideline and left a Campy chain in use for 6,000 miles. It still showed very little elongation, but a new chain skipped on the 19T cog. I found that roller displacement was a better measure of wear and now toss a chain if the distance between rollers is in the .235-.240 inch range. Shimano chains elongate so fast that they will usually reach the recommended 1/16" per foot before the rollers are shot. Shimano rollers also have about a .010 inch greater distance between them when new, so the same value isn't applicable to a Shimano (or KMC) chain.

Rather that toss that cassette with 6,000 miles on it, I just use it with any chain having at least a few hundred miles on it. No chain skip then!

[iffyjoe]

That is, the teeth of my DA cassette. Drivetrain suddenly getting pretty noisy, skipping a bit. Replaced the chain, it just gets a little worse. I took the cassette off tonight and inspected it. Amazing how tiny the teeth on all but the smallest cogs have become. Little baby teeth. I guess 15,000 miles is a real limit. Just ordered a new one.

That's a ton of miles on a DA cassette.
Get a ultegra, you'll loose a couple ounces and you can forget changing the cassette for a hell of a lot longer than 20,000 miles. Keep changing those chains however.

[Dave]

That's a ton of miles on a DA cassette.
Get a ultegra, you'll loose a couple ounces and you can forget changing the cassette for a hell of a lot longer than 20,000 miles. Keep changing those chains however.


The Ti cogs will last only about 50-60% as long as steel. I think 20,000 miles, even from steel cogs is optimistic. The life of a cassette depends a great deal on how many cogs share the most wear. Some terrains may distribute the wear of 3-4 cogs, while others might concntrate the wear on ly only one or two. I should have added that I swore off Ti cogs after wearing the 19 and 21T cogs on a Record cassette to the point where they skipped with a new chain, after only 4,000 miles. Riding in the mountains, the 19 was my most used cog, followed by the 21 (coupled with a 28T chainring!).

Changing chains too frequently only jacks up the total cost. Three more chains may cost as much or more than a cassette, so nothing is gained if you use 6 chains or more instead or 3-4. Get the most from each with careful chain management.