I had a pretty bad chain failure a couple of days ago. I bought the bike second hand about a year ago, and in all fairness I had not done much maintenance on it since. I discussed with a friend and after showing some images, he recommended to change the cassette and chainrings too. This is a nontrivial expense for me and he did not seem to be aware that the teeth on these rings are not supposed to be all exactly the same (so the recommendation might have been based on that judgment).

I have thoroughly cleaned the cassette and chainrings, but find it hard to decide if they need replacement. After some research I figured that these parts should often be replaced even before they show visual tear, so I am choosing between trying only a new chain first, or not even bothering trying the old cassette+chainrings and getting new ones straight away.

Should these parts be replaced, based on the attached images? Or should I try a new chain only first, then decide on the ride experience?

I'm pretty new to cycling (maintenance), so any advice is welcome.

Images of the chainrings:

enter image description here https://drive.google.com/file/d/171Y8GkHIazoUpsi193cJDTCLCSA303Gc/view?usp=sharing https://drive.google.com/file/d/1bEjFhXYGA7bZACvhgLaKIaeVaGxng8G9/view?usp=sharing

Images of the cassette:

enter image description here https://drive.google.com/file/d/1LyLW_y22JIImM1SidEyc9fi3ChCFKJco/view?usp=sharing https://drive.google.com/file/d/1GmMbabw11xpt9RADFe1GUCbcjix8FlpD/view?usp=sharing

Image of the failed chain:

Chain failure

  • 3
    If you are tight for money it shouldn't hurt (too much) to install a new chain and try it. The cogs are worn, but I've seen worse. Commented May 29, 2020 at 18:51
  • 2
    And I'll note that, in a few instances, I've repaired chains similarly bent (though generally not as badly) by grasping them with two pairs of pliers and twisting the bent link back straight. Commented May 30, 2020 at 0:45
  • Big ring on the front and 4th and 5th cogs in the cassette showing wear that would prompt me to expect not a great mesh with a new chain. Commented May 30, 2020 at 20:04
  • BTW, is that a 8 speed cassette in combination with two piece crank and carbon frame? I wonder if it's the correct cassette to begin with?
    – ojs
    Commented Jun 2, 2020 at 6:52
  • I count ten speeds on there
    – Pete L.
    Commented Jun 2, 2020 at 14:31

6 Answers 6


Yes. The cassette teeth are clearly worn, and the large chainring teeth have worn into characteristic shark fin shape. If you use new chain with these, it will skip. The small chainring looks still good.


To me you can try to, in this order:

  • change the chain and the largest chainring (completely worn), at least,
  • change the cassette.

You must be aware that in such a case, the best is to get a new full transmission (cassette+chain+rings), to be sure. Depending on the usage, you may then change the chain only for 2/3 times without touching rings and cassette.

If you use a new part with too older others ones, then nothing will goes very well and you will worn the new part too rapidly.


There are four options for you, from lowest cost to highest:

  1. Bend back the chain. It might eventually break, though, and risk you falling over if you are pedaling standing up at the time.

  2. Repair the chain. Either buy a separate repair link, or buy a similar enough chain and take one link from it and put it in place of the bent one. You can then ride it until it starts to skip due to wear.

  3. Replace the chain completely. This has a high likelihood of causing the chain to skip, but if it doesn't skip, it will slow down further wear of the chainrings and cassette.

  4. Replace chain, chainrings and cassette.

Apart from the falling risk of 1, there is no reason not to try 2 or 3 before replacing everything.

  • 2
    In your point 2, "master link" would make more sense than "separate repair link" Personally I keep the excess links removed when I fit a new chain, for substitutions like this.
    – Criggie
    Commented May 30, 2020 at 11:51
  • I had a chain skip off a tooth and then break the next few teeth off the cog once when I was pedaling my BSO standing up for more power, and I flew over the handlebars and got large patches of road rash on forearms and elbows. I would say to be very careful if you pick options 1, 2, or 3. In retrospect I would rather have mowed lawns or recycled aluminum cans to get the money for repairs, rather than spending several days with my arms up in the air because it hurt too much to put my hurt arms on a table or desk. If money is tight, consider looking around for a repair co-op to help fix it.
    – rclocher3
    Commented Jun 3, 2020 at 23:39

It appears that the chain has been used way beyond it's useful service life. That is, the chain stretch, is beyond 0.75%. that has caused the big chain ring and the cassette to have excessive wear. The small chain ring looks ok. You will need to change out the cassette, big chainring, and the chain. There is no easy way around this. For future reference, you should get three times the chain use per cassette. (If changed out before excessive wear). All the best in sourcing your components.


I would replace the twisted link with a master link (aka a powerlink) which is normally used as a chain joiner.

Then I'd ride the bike. I'd ride it into the ground and wear it out as far as possible. When the chains starts slipping then I'd change the cassette, chain, large-chainring, and I'd check the jockey wheels too. Yes its an expense, but you'll appreciate the difference. If saving is hard, put a dollar/euro/pound in a jar every day you go for a ride.

Once replaced I'd keep a record of mileage (strava does this for me) and keep a better handle on how long each part should go before replacement is required.

Your little chainring looks perfect, almost never used and does not need replacing.


Don't know what everyone is smoking saying that is a massively worn cassette. Only wear I see is big chainring. Even then, the teeth on the big chainring are heavily profiled so they often look worn brand new. As others have said - buy a master link and ride it.

Note: if you change chains early enough, you can easily run 4-5 chains on a single cassette & set of rings. If you let your cassette and chainrings wear too far, a new chain will slip. However, your old chain on old cassette and old chainrings might still run just fine for a LONG time still. Shifting will start to suffer before the chain starts to skip.

  • To continue on your level of politeness, pull your head out of the body orifice you have shoved it into and have a look at the shape of the teeth and the impact marks on center cogs. Those appear when the chain skips and hammers the teeth.
    – ojs
    Commented Jun 2, 2020 at 6:51
  • As someone who has flown over the handlebars and endured road rash thanks to a worn cassette and chain that I ignored when I was a broke student, I say you're nuts. It might be fine for a long time, or it might break the first time the rider applies maximum torque. Maybe shifting is already suffering, and maybe the OP isn't experienced enough to know what noises aren't normal.
    – rclocher3
    Commented Jun 3, 2020 at 23:50

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