Uninstalling worn out crank arm (no thread)

[crazytraveler]

I am at the moment with some trouble taking out the left crank arm of my bicycle. The inner thread is gone and I cannot take it out with the extractor.

Which other ways do I have for extracting it?

I am going to replace the crank arm with a new one, so I don't care if it breaks in the process, but I don't want to damage anything else.

Things I tried:

• Heat up with a hairdryer and hit it with a soft hammer. Nothing.
• Ride the bicycle 30 minutes without the screw, hoping it would get out by itself... Nothing.
  

[JimK]

maybe grabbing the crank from the outside somehow. Tricky. Here is a device that might work:

http://www.atgstores.com/automotive-specialty-tools/tekton-5692-3-jaw-gear-puller_g1815022.html

or anyway might spark another idea....

[JimK]

the ultimate fancy idea is probably to drill the crank hole a bit wider, to tap some threads into that, then thread in a sleeve that is also threaded on the inside the same way the crank should be. A lot of fuss, but... it depends a lot on what resources are available and how easily.

OK, here is another idea. Clamp the crank arm securely. Then stick a fat wooden dowel through the crank hole and tap the other end of the dowel. Nice easy knocks with a short handle ten pound sledge! With the crank arm secure you'll want the bike free to move. Like hang it from a rope somehow tied up right over the clamp.

[onrbikes]

If you can get the opposite off 1st and get the unit on a bench may be the easiest failing the puller.

Suspending the BB vertical with 2 parrallel bits of steel in between the BB and the stuck crank. You'll need to suspend the crank so the axle has a big enough space below. Then get a bar, or pin punch and give the axle (if its a solid one) a hit with a hammer. The axle will come through while the crank is still hanging.

If you're unable to take the BB out, this is another way. This is assuming its the non-ring gear side. Get a hacksaw and start sawing the Crank at the fitted end. Try to cut a slit so as to get a thin drift to pry open the hole or at least get some WD40 down it. If you get to the axle you'll know as its a lot harder. It should be pretty easy as its aluminium.

Getting the entire unit out is the best way though.

[Danneaux]

Limited time at the moment so really quick...go to the automotive parts store and buy a cheap gear puller. Get one that can be reconfigured with two or three arms. Hook the ends around the end of the crankarm and turn the screw extractor.

Hey presto, the arm will be removed without fuss. In the US, an extractor like this sells for ~USD $4 at Harbor Freight.  I've done this a number of times for others over the years,  and it is the cheapest, easiest way I know.

Hope this helps.

Best,

Dan.

[Andre Jute]

Heavy hammer and baulk of wood end on to distance hammer from your frame. This method ruins both the crank and usually the bottom bracket axle as well.

Alternatively a crank puller, as described by Dan.

However, you've had so much trouble in this area already, it might be smart to
Take it to a bike shop and ask to watch how they do the job.

[mickeg]

I assume it is stuck on a square taper bottom bracket.

If a gear puller will not work, if you have access to a Dremel Mototool, get a steel cutting wheel for that.  Cut a slot in the crank arm where it attaches to the bottom bracket.  Not a fast solution, but it is what I would try.  These are not cheap to buy, that is why I said "if you have access to ..."

If you buy a gear puller, maybe take the bike to the store so you can make sure that the jaws will fit behind the crank arm before you buy.  I have several, I think only one of mine would work and that one is a vintage model with a built in slide hammer, has not been made in years.

Gear pullers would push in on the bottom bracket.  Could damage bottom bracket.  If you can loosely fit a square nut inside for the gear puller to push on, that may save the bottom bracket.  Here in USA some hardware stores still sell square quarter inch nuts that will fit loosely in the square hole.

[crazytraveler]

Thanks for all the advice, I will see if I can find any of the tools suggested.

Heavy hammer and baulk of wood end on to distance hammer from your frame. This method ruins both the crank and usually the bottom bracket axle as well.

Alternatively a crank puller, as described by Dan.

However, you've had so much trouble in this area already, it might be smart to
Take it to a bike shop and ask to watch how they do the job.

That was how I loose the thread, last time I took it to a bicycle shop to tighten the bottom bracket they fucked up the crank arm.

After that I bought tools and a new crank arm to replace it and not need to put my bicycle in strangers hands.

[Andre Jute]

...last time I took it to a bicycle shop to tighten the bottom bracket they fubaredup the crank arm.

After that I bought tools and a new crank arm to replace it and not need to put my bicycle in strangers hands.

Same reason I learned bicycle mechanicking.

[crazytraveler]

Same reason I learned bicycle mechanicking.

 

Next time, we had the same problem in my gf's bicycle, and we went to another bicycle mechanic in another city to fix it, hopefully without breaking it.

It felt ok when riding out of the shop, but next day we continue our way and it started to creek even harder. It was Sunday. We couldn't get back, wait another day in that city, and go on Monday to complain an get it properly fixed, so we kept riding. That was the last time I took any of our bicycles to a mechanic.

[Hubs]

I've done this on a number of occasions with de-threaded crank arms - need to make sure the hooks are reasonably secure, and pop the centre bolt back into the crank arm but loose so the centre screw of the puller has something to push against. Draper puller from halfords, the smaller one, works fine, costs little. It can help, once you've got some pressure on, to give the arm a little tap to loosen it all up.

Limited time at the moment so really quick...go to the automotive parts store and buy a cheap gear puller. Get one that can be reconfigured with two or three arms. Hook the ends around the end of the crankarm and turn the screw extractor.

Hey presto, the arm will be removed without fuss. In the US, an extractor like this sells for ~USD $4 at Harbor Freight.  I've done this a number of times for others over the years,  and it is the cheapest, easiest way I know.

Hope this helps.

Best,

Dan.

[NZPeterG]

Hi All there are tools made to remove a crank with No Threads left!
Here is one (if not) the best tools made to remove your crank arm!

Note: Read and Watch the clip on how this works! it's NOT a Standard Crank Puller!

http://www.efficientvelo.com/product/stripped-crank-quick-extractor/

http://youtu.be/tbtyJIgSdPk?list=UUVo14jDYX0nhrFp6lvXht7A

Have Fun as it's an Easy Job 

Kiwi Pete 

[crazytraveler]

Hi All there are tools made to remove a crank with No Threads left!
Here is one (if not) the best tools made to remove your crank arm!

Note: Read and Watch the clip on how this works! it's NOT a Standard Crank Puller!

http://www.efficientvelo.com/product/stripped-crank-quick-extractor/

http://youtu.be/tbtyJIgSdPk?list=UUVo14jDYX0nhrFp6lvXht7A

Have Fun as it's an Easy Job 

Kiwi Pete 

64 dollars LOL

[Andre Jute]

I don't understand. If the crank will have to be replaced anyway, what's wrong with the traditional tools of choice for removing a stripped crank, a block of wood and a three-pound hammer?

[rualexander]

Or a hacksaw, cut a slot and open it out with a screwdriver, crank comes off no problem.