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Broke my chain today, why!?

james22b2james22b2 Posts: 132
edited October 2015 in MTB beginners
Hi
I was charging at full speed up a hill today when I heard a cracking noise, my gear suddenly changed and then with a second crack, the chain broke and i narrowly avoided crashing into a wall.
Why do bike chains break?
Never had this before.. guess the gears were slipping the day before, what are the pre-emptive signs for next time?
Thanks!

Posts

  • RockmonkeySCRockmonkeySC Posts: 15,247
    We're you in a gear which had your chain crossed up? Big ring at back to big at front or small to small?
  • Do you replace your chains before they are getting too worn?
  • james22b2james22b2 Posts: 132
    I guess I was in one of the higher gears at the back (out of 10) and the highest at the front (out of 2) and going at about 25kmh on a steep slope and really pedalling hard. I didn't change gear during the ascent.
    The bike is only about 10 weeks old and has probably done about 1,000km. I hadn't checked the chain before but will probably pay closer attention now..
    Had the impression before that a chain break was something that happened after years?
  • mattyfezmattyfez Posts: 638
    If your gears were slipping it suggests the chain was worn, and quite possibly the cassette too.

    How old/how many miles on the drive train?
  • mattyfezmattyfez Posts: 638
    Sorry I didn't read your reply properly, at 1000 km, the chain is almost certainly worn out.

    Age is not very important assuming it's kept clean and lubricated, but chains will wear out over that distance, they are consumable parts.
  • Some say that chain should be changed after 500 km but I think it is BS. I personally broke 2 Shimano chains, second was 150 km new in innocent situations. Bought SRAM and it last over 1500 km now. Never buy a Shimano chain again.
  • I'm bike guiding in Turkey, and I've replaced my chain once this season. The bike itself has done over 4000km or so just from myself, this year. No idea what abuse it had last year.

    Most chains that snap here, I just re-use by pushing the broken link out, and fitting a powerlink in, until the chain is truly shot, then I throw it and fit a new one. That could be more than 4000km if it's not abused too badly.

    Top tip - lube your chain regularly. It'll last MUCH longer.
  • james22b2james22b2 Posts: 132
    Thanks everyone, so I think I wasn't lubing enough so that may have been a contributing factor. Certainly never cleaned it. Will get some oil and a chain cleaner..
    I took it back to the bike shop where I bought the bike and they just stuck a link in, lubed it, and put it back on. It rides perfectly smoothly although it has a few big scratches.
    I am covering at least 100km per week at the moment so I hope it does last a while longer..
  • RockmonkeySCRockmonkeySC Posts: 15,247
    Cleaning the chain is very important if you want it to last. Putting lube on a dirty chain is pointless, you're just creating a grinding paste.
    Always clean it before lubing, wipe off excess lube so dirt doesn't stick to it and try to avoid shifting under heavy loads.
  • step83step83 Posts: 3,866
    I would get a chain wear guide wont cost much and is dead simple to use. Also means the chainring and cassette will last longer.
  • DeVlaeminckDeVlaeminck Posts: 5,991
    I doubt it broke because it was worn - certainly not after 1000k I wouldn't consider changing a chain after that distance even in Winter.

    What has probably happened is it has been damaged in use maybe a poor gear change or a stone has lodged in it or something or it could even be a manufacturing fault. The slipping may have been because it was on its way out maybe a link was twisted or cracked.
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  • RockmonkeySCRockmonkeySC Posts: 15,247
    Chain wear gauges are a waste of money. If gears are still shifting smoothly then it's fine. I get a good few thousand miles from a chain.
  • cooldadcooldad Posts: 32,904
    This ^^^^^^^^^^
    I don't do smileys.

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  • james22b2james22b2 Posts: 132
    Hi, my chain is back to behaving badly, it slipped repeatedly on my last two rides -- on the same section both times when riding hard up hill. I was sprinting in the highest gear at full pelt but not changing gear.
    Any advice for what I should say when I get round to going back to the bike shop?
  • Mad_MalxMad_Malx Posts: 4,024

    Most chains that snap here, I just re-use by pushing the broken link out, and fitting a powerlink in, until the chain is truly shot, then I throw it and fit a new one. That could be more than 4000km if it's not abused too badly.
    .

    I find this a bit worrying if you are a professional bike guide. Are you leasing bikes to your customers?
  • cooldadcooldad Posts: 32,904
    Why?

    That's exactly what I would do. I have some chains with a couple of missing links. Works fine.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • Mad_MalxMad_Malx Posts: 4,024
    Why?

    That's exactly what I would do. I have some chains with a couple of missing links. Works fine.

    As a repair to keep riding, fine, but if the chain breaks twice I think it's telling you it's time to get a new one before you wrap your nuts around the stem.
    papercut says he is a guide, which is why I ask if he's providing bikes. If so it's reasonable to expect the chain will last the day. It's not really the same as doing this on your own bike (I've used plenty of chains well past 3000km too).
  • cooldadcooldad Posts: 32,904
    Chains generally snap due to a bad change, normally a downshift under pressure, not through wear.

    A repaired one is as strong as before. although it's only one out of a hundred or so links, so maybe a bad example, I've never snapped a second time at a missing link.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

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