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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 08-16-09, 12:42 PM   #1
ChrisOG
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How much to replace a crankshaft?

A neighbor gave me a used Murray Biotech bike a few years ago. It’s my bad weather bike, I ride in the rain and snow and during the winter I usually ride at night when I get home from work. It’s not the best bike in the world, but I find it very comfortable to ride. The crankshaft went on me and I trying to decide if it’s cost effective to replace it. The rest of the bike is in decent shape.

About how much would it cost for a LBS to replace the crankshaft?
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Old 08-16-09, 01:27 PM   #2
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What do you mean, exactly, when you say crankshaft ? Do you mean that one of the crank arms is broken, or do you mean the spindle shaft that the crankset is mounted to ?
Either way, having an LBS fix it would probably cost more than the bike is worth. If it was mine, I'd find a donor bike, either a five dollar yard sale bike, or a junker from the scrap pile, and I'd fix it myself.
Sheldon Brown's website will help you learn how to do it yourself.

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Old 08-16-09, 01:32 PM   #3
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The shaft itself seems OK, it's the spindle that it's mounted to that's broken.
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Old 08-16-09, 01:41 PM   #4
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It's a simple repair, but you need the right tools. And you need a new spindle, though, like I said, I'd scavange one off a junk bike.
You need a crank puller, and the bottom bracket tools, which are likely a pin spanner, and a lock-ring spanner.
Again, check out Sheldon's site for instructions.
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Old 08-16-09, 03:47 PM   #5
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OK I have a question well several actually. are you call the part that goes through the bike the SPINDLE? if so what part are you call the SHAFT? is the part actually broken (like in two pieces) or is it just real loose and wobbly?

does this bike a have a one piece crankset or a three piece? can you post a pic?
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Old 08-16-09, 06:45 PM   #6
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I found a picture of it in Sheldon Brown's glossery, under Bottom Bracket it's the Ashtabula one piece crank. The crank itself (the part that the pedals are attached to) seems fine, it's very loose and flosts around, I think it's the bracket that holds the crank in place that's shot


Last edited by ChrisOG; 08-16-09 at 06:51 PM.
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Old 08-17-09, 02:13 AM   #7
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There's no bracket that holds the crank in place. It's the two cups, bearings and cone on each side that holds the crank in place.

Post a picture and point to the area that you think is loose.
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Old 08-17-09, 07:22 PM   #8
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I have a $250 hybrid which I've put easily another $200 into. I love the bike but wore out the drivetrain and just replaced the chain; rear cog, and now the BB (bottom bracket). It was $30 for the "overhaul" and another $30 for the BB. The bike will now be ready for another 1,000 miles and I'm glad to pay it.
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