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This is my second modern bike and I got the same problem each time. The chain slips when under load (usually when I'm standing, but I can slip starting at a light and still sitting too). At first I had an aluminum cassette and the dents broke quickly. I replaced that old cassette (that actually came off as it completely broke) with a steel cassette.

The steel cassette has been working well in the sense that the dents are still all looking good and it has not come into pieces yet, however, the chain still slips.

In both cases, I had 9-gear cassettes when I use the smallest gear 99% of the time (San Francisco type of hills still require me to change gear, otherwise, I rarely change anything, so I could assume that the small gear of the cassette gets worn down quickly...)

Would it be possible to have a cassette with longer dents to avoid the slipping? My old steel frame bikes had cassettes with really long dents, in comparison. Could a find similar cassettes that are compatible with my new bike? (I have a specialized Roubaix now)

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  • Did this behaviour start when you fitted the chain (or cassette), or have things degraded to this point? If it has always been an issue, I'd suggest either the parts are wrong or they haven't been fitted properly. If things have degraded to this point, it sounds like something is worn.
    – PeteH
    May 13, 2015 at 9:04
  • From what I recall, it started pretty quickly with my newer bike. Now it can easily happen once or twice per trip which is about 16 to 20 miles. It could be that the cassette was not well fitted from the start. At the same time, I realized that I had it for about 3 years. So it is probably time for a change anyway.
    – Alexis Wilke
    May 13, 2015 at 16:41
  • Yes, 3 years is probably beyond a change. If you have resolved to replace things (cassette and chain) anyway, make sure you get 9sp chain to be compatible with your cassette. I'd then be tempted to use first-principles to determine the length of chain to use.
    – PeteH
    May 13, 2015 at 20:42

2 Answers 2

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The chain will typically slip under the following conditions: 1. the chain is worn out (this can be measured with a cheap tool, or by your LBS). 2. the cassette is worn out 3. one or more of the chainrings (the cogs on the crankset) is worn out 4. the chain and/or cassette/cogs/pulley wheel are dirty and full of oil/road-grit/gunk.

These can occur simultaneously - a dirty chain causes rapid chain wear, a worn out chain causes the cassette to wear out. If you have been riding with a slipping chain for long, you are very likely to have worn out both the chain and the cassette and will have to replace both.

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    So... how often do you clean you chain, cassette, etc.? Do you calculate that with time, distance, weather conditions? On my old bikes, I did have to worry about that. It just worked.
    – Alexis Wilke
    May 13, 2015 at 5:09
  • I usually clean my chain before adding oil to the chain. This gets done every 200 to 400 miles, and if it rains a lot then even after 100 miles. I use smart links, so the chain can be removed and easily cleaned. Cleaning it on the bike makes a mess and doesn't really get clean when I do it, although many people do it that way. As # of gears increases tolerances go down - everything is more fussy. Maybe you would be better off with a 3-speed or single speed which you could take in for service every few months to have it cleaned.
    – Craig Hicks
    May 13, 2015 at 7:28
  • Could also be adjustment. If the chain is slipping between two gears it can sometimes feel like it's just slipping on the sprocket.
    – Holloway
    May 13, 2015 at 8:55
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    It is tedious but it is nice to have crisp shifting, and chain slip is very dangerous. If you empty your wallet and get a "carbon drive" and a "Rohloff internal gear box" you won't have to do any cleaning. I think there is also an enclosed direct drive technology - don't remember the name.
    – Craig Hicks
    May 13, 2015 at 21:32
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    @AlexisWilke as bicycles got more gears, chains got narrower and had to flex more radially. Also cogs on cassette got thinner, and made of lighter but softer materials. Result is more wear, need for more maintenance and frequent replacements. Simplest and cheapest thing you can do is to buy chain wear indicator and at least replace chain when it is time.
    – Davorin Ruševljan
    May 14, 2015 at 14:45
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I've had the problem for about 3 months across three gears. Then I got a puncture and when I fixed the rear wheel I also tightened the axel bolt. It now works perfectly. So take 30 seconds and try tightening the rear axel bolt.

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  • Too late for that one... It was really breaking down. But it's a good point that it may have started just by being a bit loose...
    – Alexis Wilke
    Mar 6, 2018 at 0:59
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    I have to say, EEEEEEK! You were riding a bike for three months with a rear wheel that was loose enough to cause gear problems?
    – David Richerby
    Mar 7, 2018 at 12:43
  • @DavidRicherby I once bought a new bike (at a LBS!!!) that for some reason simply could not tighten enough to prevent the rear wheel from turning into the frame if I pedaled hard enough!
    – Michael
    Oct 18, 2019 at 21:23

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