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I have done exactly 2879 km on my cassette, and currently I got myself a new chain which is a third for this cassette. With first chain I made 1985km, but I already noticed a significant degradation in shifting so I replaced the chain. Then with the second chain I did only 894km, but did not experienced misshifting, I just measured the chain with a chain tool (two different tools) and and it showed lots of stretch, so I replaced for the 3rd time. Now I am wondering will this chain with this much "worn" cassette last at least some reasonable time/km/miles? I have done 33km with this new chain to see how will it perform and it didn't skipped at all, I could still call it a precise shifting through all the gears, but on some cogs there's a "grinding" feel if you know what I mean. I always keep my chain, cassette and crank clean after every ride, road or off road. So would it be wise to get a new cassette at this point? Or try and see how long will this new chain last? In case someone is interested the cassette is shimano 50-9 11-34, first two chains were hg53 and the 3rd one is kmc x9.

cassette

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If in doubt, why not buy a new cassette, try it and see if you feel any improvement, and if not put the old cassette back on and keep the new one until you need it? It sounds like you're prepared to do a lot of your own maintenance and things like changing a cassette is pretty trivial when the time comes. I mean, there are (several different) rules of thumb but there's no substitute for being able to check it empirically. –  PeteH Oct 15 '13 at 20:39
    
I'm on a budget atm but I see your point. My concern was the chain and whether or not would I decrease it's life significantly. I know there are lots of folks that go by if it's not broken don't touch it, but not me, but anyhow I was interested if someone has done similar and could share the thoughts. –  user8409 Oct 15 '13 at 21:12
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It appears to be moderately worn. But why guess? Take it to a shop and have them use their tool on it to see how worn. –  Daniel R Hicks Oct 15 '13 at 21:24
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BTW, that chain and cassette are far too clean!! –  Daniel R Hicks Oct 15 '13 at 21:25
    
Did you measure the chain stretch before switching chains? Typically this is preferred over raw mileage, as mileage from a chain depends on conditions. Running a stretched chain will damage your cassette and rings. –  Rider_X Oct 16 '13 at 17:50

2 Answers 2

up vote 3 down vote accepted

By looking on the shape of the tooth on the biggest cog, it looks worn out and a time for a replacement. Grinding feeling on a clean chain is always a sign of wear.

Also worn-out cassette will will wear out chains much quicker. And you already feel that - second chain got only 50% of usage from the first chain.

I would just replace the cassette, before the new chain is also stretched out.

p.s. you are far too precise with your mileage!

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as well as logging your rides, rideWithGPS allows you to easily say when you do maintenance on your bike, so you can get geekily accurate times and distances for the lifetime of parts. Unfortunately the only actual benefit I've seen from knowing this is how many (i.e. few) miles I'm getting out of my tyres before some obstacle renders them useless! –  PeteH Oct 16 '13 at 17:38
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@PeteH I find my tyres need a replacement far less regular than chains.. And i'm tool lazy to turn on GPS every time I'm on a bike -) –  trailmax Oct 16 '13 at 23:39
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I'm always trying to be precise when it comes to mileage or anything related to cycling, and I'll take that as a compliment. ;) I'm new to this stackexchange but I suppose I have to mark the most suitable answer. –  user8409 Oct 17 '13 at 14:31

It looks like there could be some wear on the smaller cogs but it's hard to tell from the picture. It could just be the angle.

You can usually tell whether or not a cassette is worn by looking at the teeth. Each tooth should be symmetrical, like a picture-perfect mountain top. As the cassette wears, those picture-perfect mountain tops will gradually mecome asymmetrical and start to look more like shark fins. The more they look shark fins, the more worn the cassette is.

It's usually the worst and most noticeable on the smaller cogs. If you use them all equally, the smallest will wear the fastest. If you spend less time on that one, you might notice it in the second or third smallest cogs. It's pretty rare to see significant wear on the middle and big cogs without wear on the smaller ones.

The ever helpful Sheldon Brown has an article all about chain stretch and how it affects rear cogs.

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To me it appears most cogs are worn, with tell-tail notches. –  andy256 Oct 15 '13 at 22:18
    
Oops, that's tell-tale notches. I think a tell-tail is something different. –  andy256 Oct 15 '13 at 23:01

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