How to Remove a Stuck Crank Arm

My hobby is turning old track and road bikes into usable fixed and single-speed bikes. One of the most annoying problems I have encountered is stuck or broken crank arms. This advice will probably work for most BMX bikes, also.

The crank arm is the piece attached to the bottom bracket with pedals on both ends. Most bikes have one of two configurations: square shaft, or octalink. For my purposes, I'm usually dealing with a square shaft.

To prepare, remove the plastic knob from the bolt where the crank arm meets the bottom bracket. If the plastic button is stuck, simply pry it out carefully with a screwdriver. Check to make sure there's no debris inside the little chamber.

Next, use a 14mm wrench to remove the bolt. Be careful, use firm movements but do not over-exert. The worst thing that might happen is a chain-ring wound in your hand.

With the bolt removed, make sure the threading on the inside of the crank arm is clean. I suggest using a compressed air can for spraying out any debris or dust.

DISCLAIMER: Use this advice at your own risk wearing goggles and appropriate safety gear. I have hurt myself many times trying to fix a bike; this advice is meant to be considered at your own discretion.

Solution #1 - Use a crank puller

There are many excellent crank removers on the market, costing less than $15, I suggest IceToolz or Park brand. Make certain to use the correct remover; do not use a crank puller that is designed for a different bracket (octalink).

Do not strip the threads on the inside of the crank. They're not gonna grow back.

Thread the crank puller into the crank arm, insert the removal bolt, and twist. If the arm is stuck, just give the wrench a few taps with a hammer. The crank arm should pop off.

Solution #2 - Oil Soak

Most likely you've stripped the threads at this point. Not to worry, it's still possible to remove the cranks. Turn the bike on its side, so the crank is facing vertically.

Take some 3-in-One oil, available at your local grocery or hardware store, and liberally drip it into the crank where it's stuck. Wait two to three hours for the oil to fully penetrate.

If you have specialty oil, like Boeshield T-9, or Phil Wood Tenacious Oil, I suggest using that first. In a pinch, 3-in-One will suffice; don't use it on your chain.I do not suggest using WD-40; it is a water displacer and tends to seal in dirt.

Now, grab that hammer, and try to give it a whack. Be careful when you do this. The crank arm should pop off with a few solid hits.

Solution #3 - Ball Joint Remover Chisel

If the crank arm is still stuck, you may want to consider using a ball joint remover. I'm talking about the forked-chisel type.The forked chisel ball joint remover (available at most auto stores and Sears) can be placed as a wedge between the bracket and the crank arm.

I suggest using a bit of cloth to make sure the bracket is not scraped by the metal.Give the chisel a few hits with the hammer and the crank should pop off.

Solution #4 - Dremel

At this point, you're pretty angry. Don't worry, calm down.

Get out your Dremel and the fiberglass cut-off tips.

Put on your protective goggles. Seriously, put on your protective goggles.

Now, Dremel a slot into the side of the crank. You don't need to drill it all the way down to the bracket, just give it a millimeter or two.

Slide a screwdriver into the groove, and whack it with a hammer. The crank may split and buckle, cracking enough to be removed. Hopefully, this works.

In summary, I have to point out that you must practice safe repair skills at all times. Losing an eyeball because you're trying to repair a bike is not worth it.

I suggest not exerting yourself too much over a bike. It is much less frustrating to get a new bike, or ride a bike that is functional if not perfect. You can really kill your free time by having a repair project. Or, you may make something worse that would probably better be handled by a bike shop.

Finally, I do not recommend riding around a bike without the crank bolts. This is a good way to get in an accident, especially if you're an aggressive rider.