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  1. #1
    mtbr member
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    middle ring shot = new drivetrain?

    The middle ring on my crankset is shot, a broken tooth and some pretty worn teeth. The granny however and cogset seem to be ok. Mechanic at my LBS is telling me to go for a whole new drivetrain (over the phone) that I'm going to have issues if I don't. Would it be worth it just to try a new middle ring and see if it works? All I've got to lose is $20, right?

    Second issue is BB spindle. Seems to be a tiny bit of play there as well. The bike is two years old and I bought it used a year ago.(2003 Trek Liquid, stock Bonty/truvativ cranks/BB) Thinking of just replacing the BB and middle ring and riding it out for the rest of the season. Or should i just bite the bullet and go for a whole new drivetrain - cranks, BB, casstte the works?

    Trying not to spend a lot of $$$, but good deals and the inevitable are haunting me. Any advice appreciated, I'm a noob when it comes to wrenching

  2. #2
    Steep Hill
    Reputation: AZClydesdale's Avatar
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    Doesn't sound right.

    Be suspiscious if they recommend new cranks without pointing out why they are needed.

    I would consider the BB and middle ring replacement and maybe a new chain. Taking steps to wrenching your own bike will save you $$$ per year. At least do it to the point of knowing when the components are needed.

    Try keeping the cassette and chain on the same replacement schedule. If you are heavy and generate a lot of torque, replace the chain before it gets stretched so the cassette life is extended. When you see "shark fins" start to form on the teeth of your front rings, replace that individual ring.

    I change the chain, cassette, middle and small rings about twice a year. Sometimes more but only as needed.

    Just my $.02 - goodluck!

  3. #3
    mtbr member
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    thank you

    Thanks for your reply, I should probably have said specifically what my mechanic was reccommeding - chainrings, chain, cogset, and BB. He didn't say new cranks but I figured why stop there when you're replacing everything else?

    I guess there's no way of knowing for sure b/c I bought the bike used. Maybe it's time to bite the bullet.

  4. #4
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    You didn´t say what brand you have, but if it´s Shimano get a steel Deore middle ring, lasts about 4 times as long as aluminum. They can be hard to find, but I just ordered a couple from Bikeparts.com, $10 each with reasonable shipping cost. Also, get the Park Tool $10 chain wear measuring tool, you can make your components last longer if you keep a close watch on chain wear.

  5. #5
    Want to vent?
    Reputation: The SS Boz's Avatar
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    Quote Originally Posted by sweathog
    You didn´t say what brand you have, but if it´s Shimano get a steel Deore middle ring, lasts about 4 times as long as aluminum. They can be hard to find, but I just ordered a couple from Bikeparts.com, $10 each with reasonable shipping cost. Also, get the Park Tool $10 chain wear measuring tool, you can make your components last longer if you keep a close watch on chain wear.
    Agree......

    I blew thru shimano "XT" middle rings like once a year....finally bought a pricey blackspire that is taking hell and i am glad i spent the money......

    Anyways...in regards to the original post...try the ring and BB install first if you wanna save money.....a full drivetrain these days is ridiculous......specially new cassettes.....i try to run those out to every 2 chains i buy a new cassette....my .02

    -Boz
    "I'm supa-fly TNT, I'm tha guns of the navarone!"

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