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  1. #1
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    New crank advice

    Hi!
    I'm pretty new at bicycle repair and maintenance. A couple of months ago I bought an older trek 800 bike that I have been slowly rehabilitating. One component I really don't like is the crank. The existing one is in ok shape with some wear on the teeth. The cassette is in really good shape but ideally I'd like to replace that sometime in the future. One question I had, being budget minded and if I'm going to do this over time, was if I replace the crank, is it also advisable to replace the chain and the cassette? Can I just replace the crank? What's the best approach if I want to phase in this part of the bike mechanics?

    I would love to hear your thoughts! Thanks so much!

  2. #2
    Mechanic/Tourist
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    There is no need to replace chain or cassette just because you replace the crankset. But it's also more important to check the chain for wear than to replace the crank. If the chain is slightly worn you can replace it and make the cassette last longer. If it's more worn you will need to replace both at the same time. If the chain is allowed to wear to an extreme amount it can significantly wear the chainrings. Either option is more effective and less costly than crankset replacement, especially as on an older bike you may have to replace the bottom bracket along with the crank. It would be helpful in advising you if you explained why you "really don't like" the crankset, because a worn chain can cause some problems that show up in the crankset - chain suck, poor shifting, noise. It's also helpful to know where you live, as we may be able to direct you to helpful resources in your area. In-person help trumps a bunch of words online.

    Here's an excellent page from sheldonbrown.com regarding chains: http://www.sheldonbrown.com/chains.html
    Last edited by cny-bikeman; 08-26-15 at 05:35 AM.
    There's no such thing as a routine repair.

    Don't tell me what "should" be - either it is, it isn't, or do something about it.

    If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.

    Please take the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!

  3. #3
    Senior Member
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    Chainrings are far more forgiving of chain wear than cassettes, so odds are you don't have to replace the chain when you switch the crankset. However sprocket wear is higher with worn chains, so you'll always see the best sprocket life if you start with a new chain.

    You might time the crank replacement for when you're replacing the chain anyway. Or you might buy a new chain when you replace the crank, but save the old one and rotate it back into service when the new one is worn slightly more. Then you can rotate both chains leap frog style every 1,000 miles or so.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  4. #4
    Senior Member JonathanGennick's Avatar
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    I have sometimes needed to replace all three at once -- cassette, chain, crankset. Be prepared for that possibility. Try swapping in just a new crankset first if you like, but know there's a risk you may then need to replace the chain and cassette as well. I'm actually working through the opposite problem with a friend and his bike -- we swapped in new chain and cassette, and now we need to replace the chain rings.

    BTW, Jenson has Shimano Deore cranksets at $50 right now. At that price you can probably replace the entire drivetrain for under a hundred.

  5. #5
    Mechanic/Tourist
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    What FB said is accurate, and yes, it is sometimes necessary to replace the entire drive train - but the OP only indicates "some wear." But I don't think there's any sense in replacing the crankset until the chain is checked. The OP indicates budget concerns, so it is most sensible to start with the parts of the drive train that are the least costly and whose replacement gives the most benefit. Again, without knowing what about the cranks is not liked I think it unwise to advise replacing it.
    There's no such thing as a routine repair.

    Don't tell me what "should" be - either it is, it isn't, or do something about it.

    If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.

    Please take the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!

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