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How many miles will a road bike’s chain and cassette last?

Discussion in 'Road Cycling, Mountain Biking & Cyclocross' started by John Stone, Oct 7, 2014.

  1. John Stone

    John Stone Every day is Leg Day
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  2. optiks

    optiks Well-Known Member

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    Hi John,

    Out of curiosity, how often do you replace your front chain rings? I replaced my second chain at the same time as my cassette (~7000km) but didn't give much thought to the front chain rings as they weren't causing me any issues.

    I had a forced visit* to my LBS this morning however and they mentioned that they were pretty worn and probably should have been done at the same time as the cassette.

    Thoughts? How many km should front chain rings normally last?

    *I swapped from an 11spd wheel to a 10spd wheel earlier in the week and unwittingly used a 1.8mm spacer instead of a 1mm spacer, which then resulted in the chain popping off into the spokes and making a bit of a mess (the limit was presumably not set properly either). The wheel's probably had it but thankfully no damage was done to the derailleur.
     
  3. John Stone

    John Stone Every day is Leg Day
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    How many kilometers did you have on the chainring? Chainrings should last much, much longer than cassettes. If you only had 7,000 km on the chainring, I would doubt very much that it was in need of replacement.
     
  4. optiks

    optiks Well-Known Member

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    Roughly 8000km. I was surprised when he said it as he seems like an honest guy, however it's possible he was just trying to fleece me. Can you think of anything that would promote extended wear? (E.g. cross chaining, bad weather riding, ...)
     
  5. John Stone

    John Stone Every day is Leg Day
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    I'm not an expert on the subject, but I can say that I've never heard of a chainring wearing out after just 8,000 km. I've got 19,000 km on my chainring, and it's just fine (and I crosschain quite bit since Di2 is so forgiving in that department).
     
  6. optiks

    optiks Well-Known Member

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    Thanks, 'tis a bit odd. Let's go with too much power as the cause.
     
  7. John Stone

    John Stone Every day is Leg Day
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    I like that. :lol:
     
  8. abuseguy

    abuseguy Active Member

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    My rule of thumb for replacing chainrings is to test ride the bike after replacing the chain. If the new chain skips on the power stroke, it's time for new chainring(s). You can also see if the chain isn't able to "settle down" all the way on the cogs before riding.

    Here's the flipside to my technique: If chainrings are relatively worn but not yet skipping, chains will wear out sooner because the "points" on the gears are farther apart. Since the chain has to work harder to settle down on the chainring, it will stretch sooner.

    Many mechanics (me too!) eyeball chainrings, but I only use this as an argument for replacement if they are very worn. Especially on mt. bikes, the chainring teeth will start to wear so the front side of each tooth is curved, such as seen in the following picture. (http://pardo.net/bike/pic/fail-016/Worn_chainring.jpg) You will also see that the teeth become "pointed" at the top, without a rounded peak, and very wide "valleys." There are also gauges for chainrings and cassettes.

    If you want to extend the lifespan of chainrings and you have ones that are bolted to the cranks with Allen bolts -- most good bikes do -- periodically unbolt and rotate the chainrings forward on the crank, perhaps every other time you change the chain. By doing this, peak exertion isn't applied to the same chainring teeth for the life of the component: the wear is spread out over the circumference.

    The tool that John recommended is a good one, but use it gently. If you bend the pin, the accuracy is gone. The same applies to nearly all chain wear gauges -- they can be a tad delicate.
     

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