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Broken chain due to worn cassette?

JavierRodJavierRod Posts: 5
edited June 2019 in MTB general
Hi guys,

One day while riding my chain broke, so I took it to the shop and they said they had to replace it but also check the cassette, if the cassette is worn could it break a new chain?

Please help out I don’t want to pay for a new cassette if not necessary.

Thanks in advance!



  • bondurantbondurant Posts: 858
    Not break the chain but cause it to wear quicker than it should.
  • cyclecliniccycleclinic Posts: 6,865
    Chains often break due to excessive wear. That means the cassette is too worn to be used with a new chain.

    Unless you know that cassette is fresh then replace it. I'd say anyone placing a wager that the cassette is fine would be losing that bet. -wheel building and other stuff.
  • fenixfenix Posts: 5,437
    If the chain stretches then it wears the sprockets faster as it's not quite matching up with the teeth on the sprocket.

    Your cassette costs more than the chain so its good practice to replace the chain before its stretched too much.

    We don't know the state of your cassette. I'd google pics of cassettes and compare to what yours looks like. Wear is pretty obvious.

    I'd prob try the new chain and just be aware that it takes a few miles to bed the chain in on a cassette that maybe slightly worn.

    Chain checker and keeping the chain clean both help.
  • steve_sordysteve_sordy Posts: 2,438
    How old is the chain? If you have no idea, then it is probably worn out. You can buy an inexpensive chain gauge to keep an eye on your new chain in future.

    A worn chain can rapidly wear out everything else it touches, such that even when you put a new chain on, the gears won't run well with the new chain. Symptoms would include the chain slipping when you put any pressure on the pedals, not a pleasant feeling. This is why the shop advised to check the cassette. The teeth on worn cassette gears may have burrs on them where the metal has been forced over the sides. The burrs will slow down the shifting and may cause all sorts of other problems. The root between the teeth may be elongated, ie not round where the chain roller sits, but flat. That is caused by the tooth face wearing away. I would also check the jockey wheels. The jockey wheels may look more like ninja throwing stars! New jockey wheels are easy to fit and cost about a tenner.

    A chain can break, but I doubt that it is because it is worn unless the wear is of epic proportions! One of the the main causes of a broken chain is poor gear selection. What do I mean by poor? If you have a triple gear up front, you might be in the big gear at the front and the big gear at the back*. Running like that is called cross hobbling and it is very bad for the chain as it tries to peel apart the sideplates. If you then try shifting under load, say from the big front ring to the small front ring, then even a brand new chain could tear apart. I've seen it happen - the chain peeled apart and the small gear at the front got bent when the chain jammed and the guy had full pressure on the pedals. It also gouged the frame!

    Note* Running small to small has a similar effect, but not quite as bad. But you may drop the chain if going over rough ground because there is so much loose chain flapping about. When the chain comes off the front ring (it is nearly always the front), then it may jam and if you have full pressure on the pedals it may break or cause damage to your bike.

    Another big cause of chain breakage is shifting under load. Some systems can cope with this better than others when new, but it is never a good practice. When shifting, always try to time the shifts such that you can back off the pressure slightly to allow the chain to move from one gear to another without being under load.

    Running the chain in the proper gears, not shifting under load, keeping the chain clean and lubed, regular checking with your chain gauge; all of these will extend the life of your chain. More importantly, this will extend the life of the rest of your drive train, which is even more expensive than your chain. You should get three chains used up before the cassette needs replacing.
  • robertpbrobertpb Posts: 1,866
    In a muddy year I've gone through 2 cassettes and 5 chains one was a cheap chain, but was not cheap in the long run. Too many people who are are new to cycling seem to think that a chain will last the lifetime of the bike, I remember a post on here when someone had owned the the bike for over two years and was angry that the shop had told him that a new chain was needed.

    Last year I remember talking to a guy in London with a red rusty chain that was squealing, "you need to oil that" I said. It transpired that he rode the bike every day and had never oiled the chain.
    Now where's that "Get Out of Crash Free Card"
  • JavierRodJavierRod Posts: 5
    Thanks for all the help!

    My bike has around 700 miles, I haven’t replaced anything since I bought it, but I give it regular
    I live in Costa Rica, so I often ride in mud or very dirty tracks. Hills are pretty rough so I also often use 1x1, from my 2x11 SLX.
  • steve_sordysteve_sordy Posts: 2,438
    JavierRod wrote:
    .............My bike has around 700 miles, I haven’t replaced anything since I bought it, but I give it regular Maintenance.
    I live in Costa Rica, so I often ride in mud or very dirty tracks. Hills are pretty rough so I also often use 1x1, from my 2x11 SLX.

    Then the chain is probably knackered!
  • cyclecliniccycleclinic Posts: 6,865
    your chainrings might be toast too. -wheel building and other stuff.
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