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  1. #1
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    Help with my trek 4300 crank arm.

    So I'm going to purchase a Trek 4300 secondhand from a friend but the left crank arm (i think its these ) is stripped on the inside where it connects to the bottom bracket. The inside is a square hole and it looks like its stripped from usual wear and tear, I think the crank arm is aluminum. It wont hold still for more then two seconds (it loosens the bolt) any quick fixes?
    Thanks in advance for your help.

  2. #2
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    No quick fixes -- you need a new crank arm. See if a local shop has a used or take-off left arm kicking around that they can sell you for cheap.

  3. #3
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    Quote Originally Posted by mconlonx View Post
    No quick fixes -- you need a new crank arm. See if a local shop has a used or take-off left arm kicking around that they can sell you for cheap.
    I was afraid of that.. Dammit!

    Thanks for the help though

  4. #4
    Senior Member Retro Grouch's Avatar
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    If you're not picky about having a perfect match it's actually not too expensive. All of the shops that I've worked at kept a generic spare or two on hand. They sell in the $15.00 to $20.00 range. One thing to be careful of is the orientation of the hole. There's diamonds and there's squares. If you get the wrong one it'll make for a real funny pedaling gait.

  5. #5
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    Quote Originally Posted by Retro Grouch View Post
    If you're not picky about having a perfect match it's actually not too expensive. All of the shops that I've worked at kept a generic spare or two on hand. They sell in the $15.00 to $20.00 range. One thing to be careful of is the orientation of the hole. There's diamonds and there's squares. If you get the wrong one it'll make for a real funny pedaling gait.
    I'm not too picky, I've been trying to fix it with everything from liquid nails to tape
    I'm gonna try and buy some locktite supposedly its superb.

  6. #6
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by Alex carnavas View Post
    I'm not too picky, I've been trying to fix it with everything from liquid nails to tape
    I'm gonna try and buy some locktite supposedly its superb.
    First - Do no harm.

    Don't do anything to screw up your BB spindle or you'll have two components that need replacing.

  7. #7
    Senior Member mixtemaniac's Avatar
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    is that a isis, octalink or square taper bottom bracket? I can't tell from the picture. Although, usually when the crank is stripped, the bottom bracket interface is too. Especially square tapers. It comes from repeatedly tightening the crank too hard, removing it and then tightening too hard again.

  8. #8
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    Quote Originally Posted by mixtemaniac View Post
    is that a isis, octalink or square taper bottom bracket? I can't tell from the picture. Although, usually when the crank is stripped, the bottom bracket interface is too. Especially square tapers. It comes from repeatedly tightening the crank too hard, removing it and then tightening too hard again.
    I think the one in the picture has eight mine is square though.

  9. #9
    Senior Member mixtemaniac's Avatar
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    if yours is square, there's a good chance that the bottom bracket spindle is also worn.

  10. #10
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    The model number and length are usually stamped on the inside of the arm.
    Here are a few. http://www.loosescrews.com/index.cgi...d=988287520832
    And here: http://www.bikeparts.com/productsear...oryName=CRANKS - INDIVIDUAL ARMS

  11. #11
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    Thanks for all the help and replies. Also are there an steel/aluminum hybrids out there that will handle a hell of a beating but still be lite ?

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