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  1. #1
    mtbr member
    Reputation: Duvers's Avatar
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    What drivetrain parts to replace and when?

    Hi! I have a "2006 Stumpjumper FSR Expert Women's" that I bought new in July 2007. Put lots of miles on it, but never knew/thought about replacing drivetrain parts. When I began building a new bike up over the winter, I learned about chain stretch and wearing out drivetrain components.

    Anyway, I now know that I *totally* overstretched the chain and caused the cassette teeth to cup on one side from the chain stretch. I want to go through the drivetrain components and replace what's needed, but not sure about when/if I should replace certain components. Please weight in:

    • Chain (know I need to replace)
    • Cassette (know I need to replace)
    • Bottom bracket (do you replace this intermittently, or wait til you need to?)
    • Chainrings (Should they be replaced when cassette is?)
    • Der. cables (should be replaced)
    • Rear der. pulley "wheels" (Should these be replaced intermittently?)

  2. #2
    ~Disc~Golf~
    Reputation: highdelll's Avatar
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    looks like you pretty much got it.

    BB - only replace if broken/ worn.
    Some PM will add to its lifetime.

    Rings- replace if you see any 'shark-finning' or if you're developing alot of chainsuck.

    Pulleys (jockey-wheels) - replace if worn or noisy (clickity) - again, some PM will add many miles to these.
    Honestly, you just take a deep breath and say Fuck it.

  3. #3
    Off the back...
    Reputation: pinkrobe's Avatar
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    Yah, what highdell said. If you replace your chain before it's too far gone, you can prolong the lifespan of the cassette and chainrings significantly.

  4. #4
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    OK, so rings don't need to be replaced unless "shark finning" (good description, BTW), even if the cassette teeth have "shark finning" going on. I'll look at them more closely to see how the teeth look.

    Thanks for the info!

  5. #5
    Former Bike Wrench
    Reputation: mtnbiker72's Avatar
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    -If you replace your chain at 12 1/16" (measured pin to pin), you should be able to go through 4 or 5 chains before having to replace the cassette.
    -If your chain is at 12 1/8" when you replace it, replace the cassette as well.
    -If your chain is >12 1/8" when you replace it, count on replacing the cassette and chainrings.
    -Service your Bottom Bracket (see Sticky for external bearing service)
    -Replace derailleur cables and housing
    -Derailleur pulleys last a long time, but its good to pull them off and lubricate the bearings/bushings occasionally.

  6. #6
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    Quote Originally Posted by Duvers
    OK, so rings don't need to be replaced unless "shark finning" (good description, BTW), even if the cassette teeth have "shark finning" going on. I'll look at them more closely to see how the teeth look.

    Thanks for the info!
    I think if you see shark fins it's likely you'll experience chain suck, too. However, it's unlikely that all your chain rings will need to be replaced. Most people put the majority of wear on their middle ring with the little and big rings getting much less wear. If this is the case and it's only your middle ring that's bad there's really no reason to replace the big and little rings.

    How's your brake pads? They're a wear item. Check your rotors, too. Wheels true with no wobble or humps and good spoke tension? Tires in good shape? Front shock doing ok? Check your wiper seals and give them some TLC. Same with the rear shock. Tires in good shape? Hubs running good?

  7. #7
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    Reputation: RustyIron's Avatar
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    Quote Originally Posted by Duvers
    OK, so rings don't need to be replaced unless "shark finning" (good description, BTW), even if the cassette teeth have "shark finning" going on. I'll look at them more closely to see how the teeth look.
    That's not necessarily true. If the teeth look bad, they are bad. But if they look pretty good, they might still give you problems. Put the bike together, and if you end up having problems with those chain rings, then you know right where to go. I've never run a chainring that looked bad, but they always start sucking or having other shifting problems while they still look good.

    If changing these parts and mechanics are a big deal to you, you might want to consider changing the parts now, rather than letting the project drag on.

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