What you need to remove a crank

A bicycle crank comes off with three tools: a crank puller (a threaded tool that pushes the crank arm away from the spindle), an Allen wrench or wrench that fits your crank bolt, and sometimes a socket wrench depending on your crank type. The crank puller is the essential one—you cannot remove a crank safely without it, and trying to hammer or pry it off will bend the arm or damage the threads where it attaches to the spindle.

Most modern bikes use either a square-taper crank (older, more common on entry-level bikes) or a splined crank (newer, found on mid-range and higher bikes). The removal process is nearly identical, but the crank puller you buy must match your crank type—they are not interchangeable. A bike shop can tell you which one you have in seconds, or you can look at the hole in the center of the crank arm: square-taper holes are visibly square-shaped, while splined holes have multiple small grooves around the edge.

Key Takeaways

  • You must use a crank puller tool specific to your crank type (square-taper or splined)—attempting to remove a crank without one will damage it.
  • The crank bolt or nut comes off first with an Allen wrench or socket wrench, then the crank puller threads into the crank arm and pushes it off the spindle.
  • Both crank arms must be removed together as a unit because they are fixed to the same spindle; you cannot remove one without removing the other.
  • If the crank bolt spins without loosening, the spindle is turning inside the bottom bracket—you will need to hold the spindle still with a second wrench before you can proceed.

Removing the crank bolt or nut

Start by flipping your bike upside down or placing it in a repair stand so you can access the crank arms from below. Locate the bolt or nut on the non-drive side (the left side when you are sitting on the bike). This fastener holds the crank arm onto the spindle.

Use your Allen wrench or socket wrench to loosen this bolt counterclockwise. If the bolt spins without coming loose, the spindle itself is rotating inside the bottom bracket. When this happens, hold the spindle still by placing a second wrench on the opposite side of the bottom bracket (on the drive side, where the chainring is) and turning it slightly to lock the spindle in place. Then return to the non-drive side and finish loosening the bolt.

Once the bolt is loose enough to turn by hand, remove it completely and set it aside. Some cranks have a dust cap covering the bolt—if yours does, pry it off gently with a flathead screwdriver before you start.

Threading in the crank puller

The crank puller has a large outer sleeve that threads into the crank arm, and a center screw that does the actual pushing. Thread the outer sleeve into the hole in the center of the crank arm by hand first, turning it clockwise until it is snug. Do not force it—if it does not thread smoothly, you may have the wrong puller for your crank type.

Once the sleeve is hand-tight, use an adjustable wrench or the wrench that came with your puller to tighten it another half-turn or so. It should be firm but not cranked down with all your strength. The threads in the crank arm are aluminum and strip easily if you overtighten.

Pushing the crank off the spindle

Now turn the center screw of the crank puller clockwise with an Allen wrench or the handle provided. This screw pushes against the spindle and forces the crank arm away from it. Turn slowly and steadily—you should feel resistance, and the crank will gradually slide off the spindle.

Stop turning once the crank arm is loose enough to wiggle by hand. Do not keep turning after that point; you risk stripping the threads in the puller. Remove the puller by unscrewing the outer sleeve counterclockwise, then slide the crank arm the rest of the way off by hand.

The spindle will now be exposed on one side. To remove the other crank arm (the drive side), repeat the same process: remove its bolt, thread in the puller, and push it off. Both arms come off together as a unit because they are fixed to the same spindle.

What to do if the crank is stuck

If the crank will not budge even with the puller turning steadily, stop and do not force it further. A stuck crank usually means corrosion has built up between the crank arm and the spindle, especially if the bike has been exposed to rain or salt.

Spray penetrating oil (such as WD-40 or a similar product) around the base where the crank arm meets the spindle. Let it soak for 15 to 30 minutes, then try the puller again. If it is still stuck after a second attempt, the crank may require professional removal—a bike shop has access to heat and specialized tools that can free a severely corroded crank without damaging it.

Reinstalling the crank

To put the crank back on, slide the crank arm onto the spindle by hand, making sure the splines or square taper align. The arm should slide on smoothly without forcing. Once it is seated, thread the bolt back in by hand first, then tighten it with your wrench. Tighten firmly but do not overtighten—most crank bolts should be snug enough that the crank does not wiggle, but not so tight that you risk stripping the threads.

After reinstalling, grab the crank arm and try to move it side to side. If there is any play or wobbling, the bolt is not tight enough. If the crank feels solid and does not move, you are done.

When to call a professional

If you do not have a crank puller and do not want to buy one, a bike shop can remove and reinstall your crank for a small fee—usually between $15 and $40 depending on the shop. This is worth doing if you are only removing the crank once or twice.

You should also have a professional handle the job if the crank is severely stuck, if the bolt keeps spinning no matter what you do, or if you are unsure whether your crank is square-taper or splined. Attempting removal without the right tool or knowledge can permanently damage the crank arm or the bottom bracket.

Frequently Asked Questions

Can I remove just one crank arm?

No. Both crank arms are attached to the same spindle, so removing one requires removing the other. If you only need to access one side (for example, to replace a chainring on the drive side), you still have to take off both arms.

What is the difference between square-taper and splined cranks?

Square-taper cranks have a square-shaped hole in the center and are found on older and budget bikes. Splined cranks have multiple small grooves around the hole and are standard on newer and higher-end bikes. The removal process is the same, but you must use the correct crank puller for your type.

Do I need to remove the chain before taking off the crank?

No. The chain can stay on the chainring while you remove the crank. However, if you are also removing the chainring or bottom bracket, you may want to take the chain off first to avoid getting grease on your hands or clothes.

How tight should the crank bolt be when I reinstall it?

Tight enough that the crank does not wiggle side to side, but not so tight that you need a wrench to turn it further. Most crank bolts are torqued to between 35 and 55 newton-meters, but hand-tight plus a firm quarter-turn is usually sufficient for home maintenance.

What if I lose the crank bolt?

You will need a replacement bolt that matches your crank type and spindle diameter. Take your crank or spindle to a bike shop and they can match you with the correct bolt, usually for a few dollars. Do not use a random bolt—it must be the right length and thread pitch or the crank will not seat properly.