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Old 12-29-10, 12:43 PM   #1
Alex carnavas
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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.
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Old 12-29-10, 12:57 PM   #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.
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Old 12-29-10, 01:15 PM   #3
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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.
I was afraid of that.. Dammit!

Thanks for the help though
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Old 12-29-10, 01:33 PM   #4
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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.
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Old 12-29-10, 04:11 PM   #5
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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.
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.
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Old 12-29-10, 04:18 PM   #6
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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.
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Old 12-29-10, 04:44 PM   #7
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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.
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Old 12-29-10, 08:44 PM   #8
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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.
I think the one in the picture has eight mine is square though.
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Old 12-30-10, 12:08 AM   #9
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if yours is square, there's a good chance that the bottom bracket spindle is also worn.
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Old 12-30-10, 09:29 AM   #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
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Old 12-30-10, 11:38 AM   #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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