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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 08-19-07, 07:21 AM   #1
mike
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Help! I stripped the threads on the crank - can't remove it.

Oh man, how did this happen? I was using my Park crank extractor tool. I made sure that it was threaded all the way into the crank arm, but when I went to remove the crank, the threads tore off the crank rather than the crank arm coming off. And YES, I had to use a lot of muscle to do it and YES, I did make sure the bolt was off before I tried to remove the crank arm.

Now what to do? There seem to be some footprint rememants of some threads remaining

Any ideas?

I am thinking about cutting the crank arm off. Has anybody ever tried this?
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Old 08-19-07, 07:33 AM   #2
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I picked up a used bike that had a stripped out arm. I heated the arm & tapped it off with a hammer.

I'm not sure that this is the best option, but it worked for me.

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Old 08-19-07, 07:37 AM   #3
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Wow, hard to imagine this sort of thing happening to a veteran bike dude like yourself. What kind of crank is it, some campy and stronglight cranks use a slightly larger diameter puller. Probably too late to use the correct size even if that's the case.

Theres a tool for auto mechanics used for disassembling ball joints, affectionately called a pickle fork by some. It's a two prong fork with wedge shaped tines that slip between the crank and the bottom bracket. You insert it and whack away at it with a hammer. Brutal and marginally effective, but I have seen it work.

Other folks will tell you to ride the bike with the bolt off and it'll loosen itself. I personally haven't seen that work, but it's worth a try.

Or, use a hacksaw and just cut the b/b spindle and buy a new one.
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Old 08-19-07, 07:43 AM   #4
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use a piece of wood about 1inch diameter n 1 ft long and a mallet. try to bang it out from the other side.heating it might work but its too troublesome.
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Old 08-19-07, 07:45 AM   #5
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There are a bunch of posts on this. I remember reading 3 or 4 methods, culminating in the "proper sized socket on a concrete floor" method.
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Old 08-19-07, 07:54 AM   #6
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Theres a tool for auto mechanics used for disassembling ball joints, affectionately called a pickle fork by some. It's a two prong fork with wedge shaped tines that slip between the crank and the bottom bracket. You insert it and whack away at it with a hammer. Brutal and marginally effective, but I have seen it work.
There's another, and better tool for auto mechanics that I used (on a non-drive side mind you) crank arm the other day that came into the shop with no threads and needed a BB repack:

What you need is a pulley-puller:



Be sure to put an old crank bolt in the threaded hole on the BB to press against so you don't wreck the threads in the BB (and leave it a bit loose so the arm can acually move!)
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Old 08-19-07, 08:15 AM   #7
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Quote:
Originally Posted by I_bRAD View Post
There's another, and better tool for auto mechanics that I used (on a non-drive side mind you) crank arm the other day that came into the shop with no threads and needed a BB repack:

What you need is a pulley-puller:



Be sure to put an old crank bolt in the threaded hole on the BB to press against so you don't wreck the threads in the BB (and leave it a bit loose so the arm can acually move!)

WOW, Cool pick! Thanks.

For the other posts, I did try the "bang on the crank with a hammer" technique in my early days wrenching. The net result was breaking the cups in the BB, so that technique probably will stay in retirement for now.
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Old 08-19-07, 08:22 AM   #8
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crank of flywheel puller for combustion engines might work.

also, i've used a crescent wrench (metric is preferred) and a hammer for similar situations in the past (not with bike cranks tho).

was this a suntour crank? same thing happened to me.
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Old 08-19-07, 08:24 AM   #9
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Any chance there was a washer behind the fixing bolt that you didn't remove? Leaving the washer in can produce just the results you experienced.
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Old 08-19-07, 08:48 AM   #10
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... What you need is a pulley-puller ...
Also called a bearing puller - used for wheel bearings. I point this out because they are usually smaller - closer to the size it seems you may need.
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Old 08-19-07, 08:49 AM   #11
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... also, i've used a crescent wrench (metric is preferred) ...
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Old 08-19-07, 09:21 AM   #12
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If the BB is cup and cone remove the crank/spindle assembly from the bike (I'm assuming you have one side off) by removing the appropriate cup. Take this assembly to your bench vise and position it in the open jaws so the inside end of the cup is resting on the top of the open jaws. Apply some penetrating oil and give the end of the spindle one or two good, solid whacks with a BFH and punch. Watch your toes.
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Old 08-19-07, 09:25 AM   #13
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also, there is this stuff called freeze off. you spray it on parts that are seized up. it freezes them, they contract, then its easier to remove them.
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Old 08-19-07, 09:52 AM   #14
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HillRider is likely correct about the washer. And I also agree with Noam and his suggested technique. If it is a sealed bb, just try riding it around the block a few times.
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Old 08-19-07, 10:01 AM   #15
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Another option, though not cheap is the Stein Crank Extractor System.
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Old 08-19-07, 10:20 AM   #16
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You need a pitman arm remover. They come in two or three sizes, you need the small one.
They are cheap to buy and easy to use. And if you put a rag behind the crank it wont mar the finish.
http://images.google.ca/imgres?imgur...%3Den%26sa%3DN
Been there, done that.
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Old 08-19-07, 10:28 AM   #17
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if you can find one of these



they work excellent. Be sure to wrap a hose clamp arounf the puller arms once they are in place, this will keep them in place during extraction.
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Old 08-19-07, 10:42 AM   #18
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Quote:
Originally Posted by tellyho View Post
There are a bunch of posts on this. I remember reading 3 or 4 methods, culminating in the "proper sized socket on a concrete floor" method.
Voila

Find a socket that just fits inside the square of the crank arm.

Put the socket on a cement floor.

Place the bike over the socket so the socket is inside the square of the crank arm. Have someone hold the bike.

With a flat punch and a BFH (big f@cking hammer), hammer on the crank arm as close as you can to the bottom bracket. Put a big flat washer between the punch and the crank arm to protect the soft metal.


Works every time.
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Old 08-19-07, 11:27 AM   #19
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Did you by chance leave the screw in piece with the oversize end on while you were trying to remove the crank? I bet that is what happened. It is oversize and won't fit down to the crank spindle. All the strength you applied went into trying to force the threaded part out of the crank and guess what. I had a friend do that one day with my tools. Wouldn't let me help him. I guess the 2 Guiness Stouts post ride didn't help either...Send me a PM and I will send you some photos of the setup I used.
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Old 08-20-07, 06:43 AM   #20
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cyclus,var and stein make tools for this problem,it reams out the old threads and taps in an over size thread and uses an over size crank extractor.
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Old 08-20-07, 07:08 PM   #21
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SUCCESS! …if you can call it that. I totally destroyed the crank arm in order to replace it. I am not exactly sure why I felt compelled to remove the crank arm in the first place. After all, it was secure to the BB spindle. I guess I just wanted the left crank to match the right crank. How vain.

Anyway, I couldn't find anybody with a pulley puller. I used a disc cutter to cut through the crank arm down to the BB spindle. Then, I pounded a thick screwdriver into the slit using it as a wedge. Then, I heated the screwdriver up with a torch the slit and break the last thin layer of crank arm aluminum so that I would not have to cut and ruin the spindle.

Then, I heated used a punch awl (actually an old pedal spindle), and a hammer and gave it a WHACK from the other side. FLIIIIIING, it came right off.

Ugh. Cutting up good parts is not in my nature. BUT, it's done. Hmm. Done it is. Now to put on the new crank. Hope it fits....
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