When do you replace cogs?

Measuring cassette wear is a pain, it's easier to indirectly check it by inspecting your chain regularly. The cassette (obviously) is worn out by the chain, so if you make sure the chain is never too worn, the cassette won't be too bad either.

Measure 12" worth of chain, and see how long it actually is -- 12 1/16" or over, and you should replace your chain. Any more than 12 1/8" and it's likely too late, and both the chain and cassette are worn, and both will need replacing.

But anyway.. worn cassettes .. I go by the highly scientific gauge of "the shifting very quickly goes to rat-[censored] when you put a new chain on" 😉

How have you been with chain cleaning, etc. over those 3,000 miles? Have your rides been unusually dusty/wet/etc.?

in my own experience after 3,000mi/~5,000km I'd be seriously checking my chain as it's probably almost used up. But your local weather, maintenance regimen, and riding conditions can vary this considerably. As an extreme example, I've had chains on a mountain bike last less than 1,000km!

rek said:

Measuring cassette wear is a pain, it's easier to indirectly check it by inspecting your chain regularly. The cassette (obviously) is worn out by the chain, so if you make sure the chain is never too worn, the cassette won't be too bad either.

Measure 12" worth of chain, and see how long it actually is -- 12 1/16" or over, and you should replace your chain. Any more than 12 1/8" and it's likely too late, and both the chain and cassette are worn, and both will need replacing.

But anyway.. worn cassettes .. I go by the highly scientific gauge of "the shifting very quickly goes to rat-[censored] when you put a new chain on" 😉

How have you been with chain cleaning, etc. over those 3,000 miles? Have your rides been unusually dusty/wet/etc.?

in my own experience after 3,000mi/~5,000km I'd be seriously checking my chain as it's probably almost used up. But your local weather, maintenance regimen, and riding conditions can vary this considerably. As an extreme example, I've had chains on a mountain bike last less than 1,000km!

Thanks for the response. Most of those 3,000 miles were on extremely flat areas. I've cleaned the chain several times, but probably not nearly enough. I'll measure the chain and go from there.

if you replace the chain more often you will not need to replace the cassette as often. For me, i replace the chain 2-3x per year and the casette anually. As long as i keep tabs on the chain wear i do not detroy my cassettes. With that being said there is a good chance you will need a cassette, chain and maybe even front rings depending on how bad they are worn.

Stephen B said:

Thanks for the response. Most of those 3,000 miles were on extremely flat areas. I've cleaned the chain several times, but probably not nearly enough. I'll measure the chain and go from there.

If you've kept the chain reasonably lubed, say relubing every 100 miles, the wear may not be excessive yet. It's easy to measure wear as rek said, so there is no need to replace it by guessing or going by some fixed mileage schedule. You can buy a Park CC-3 "Chain Checker" for about $10 that makes wear measurement simple and quick. It's just a small go/no-go gauge, with two sides. One is set for minimum wear, 0.75%, the other for 1.0%. When it drops into the chain, it's time.

Agree chain life depends a lot on where you ride, even if you keep it properly lubed. A dusty or sandy environment is going to create more wear than a clean one. Just as one data point, I changed my PC-99 chain early this year when the gauge said 0.75% wear, which was at 6000 miles. I'll be disappointed if the DA cassette doesn't last for at least 3 chains, or 18K miles.

But, I'm a low-torque rider with a triple; more of a spinner than a grinder. I use the big cogs more than I do my 12-13-14, so there are normally plenty of cog teeth to share the load.

Shifting by itself would indicate to me the RD needs adjustment, or the cable is binding, or the shifter head itself is messed up. A competent mechanic ought to be able to determine the problem and solution in a few minutes.

dhk said:

If you've kept the chain reasonably lubed, say relubing every 100 miles, the wear may not be excessive yet. It's easy to measure wear as rek said, so there is no need to replace it by guessing or going by some fixed mileage schedule. You can buy a Park CC-3 "Chain Checker" for about $10 that makes wear measurement simple and quick. It's just a small go/no-go gauge, with two sides. One is set for minimum wear, 0.75%, the other for 1.0%. When it drops into the chain, it's time.

Agree chain life depends a lot on where you ride, even if you keep it properly lubed. A dusty or sandy environment is going to create more wear than a clean one. Just as one data point, I changed my PC-99 chain early this year when the gauge said 0.75% wear, which was at 6000 miles. I'll be disappointed if the DA cassette doesn't last for at least 3 chains, or 18K miles.

But, I'm a low-torque rider with a triple; more of a spinner than a grinder. I use the big cogs more than I do my 12-13-14, so there are normally plenty of cog teeth to share the load.

Shifting by itself would indicate to me the RD needs adjustment, or the cable is binding, or the shifter head itself is messed up. A competent mechanic ought to be able to determine the problem and solution in a few minutes.

DHK, As frequently as these threads pop up, wouldn't it be a great idea if the admins would make some kind of "sticky" so that we wouldn't have to keep posting the same info all the time?

It's a known fact that newbs don't know how to use a search function. It's covered 1000 times in old threads.

Here's a link with some photos of chains and cog engagement which tried to show what a worn chain/new cog, or worn cog/new chain look like.

http://www.sheldonbrown.com/chains.html

replace cogs and maybe chains when you start getting skipping. but if your derailleur is "shifting" all by itself, i'd guess that you may have some tension problems. are you using a friction system. if so, tighten it up a bit.

Doctor Morbius - with over 1200 posts in a couple of years, i'm sure you know this forum inside and out. i've only been around a couple of months, but let me be frank in saying that i'm already getting tired of hearing you dis newbies because they either don't notice a very inconspicuous search function or don't have the free time to go through 197 pages of old posts.

dhk's been around longer and made more posts, always informative and un-smug. sounds like a nice guy to go for a ride with. how about lightening up a little?
instead of dissing new members, how about contacting the admin and suggesting a change to make the board better. have you done that?

O.K. I've measured the chain and it seems to be the right length. I did a thorough cleaning and lubing today - I also tighted the barrel adjustment on the cable. Then I took her out for 20 miles (was supposed to be 24, but the flat I got ended that!). This helped a little bit. Now it only slips between the 3rd and 4th gear when I'm on the larger front chain ring. Before the cleaning, it was jumping gears at several combinations.

I can't get into a shop for another week or two - so hopefully, I can live with it until I can get it fixed by a pro.

Thanks for all the help.

large ring up front and third and forth in the rear; most people's most commonly used gears. sounds like those are all you need to replace. it's not at all a hard job to do yourself. maybe get a repair book and the right tools instead of paying someone else. of course, if you've got a really cheap crank set that you can't just replace the rings, you ought to upgrade.