You need a crank puller tool and an Allen wrench or wrench set to remove cranks safely
Bicycle cranks come off in two stages: first you remove the crank arm bolt (or bolts), then you use a crank puller to separate the arm from the spindle. The crank puller is essential—trying to pry or hammer a crank off without one will strip the threads on the spindle or crack the crank arm itself. You can rent a crank puller from most bike shops for a few dollars, or buy one for $15 to $40 depending on the type.
The process takes 15 to 30 minutes once you have the right tools. The spindle (the axle the cranks attach to) stays in place; you are only removing the arms. If you need to replace the entire crankset or bottom bracket, that is a separate job.
Key Takeaways
- A crank puller is the only safe way to remove a crank arm; you can rent one from a bike shop or buy one for $15 to $40.
- You must remove the crank arm bolt first using an Allen wrench or wrench, then thread the puller into the crank arm and turn the center screw to pop the arm off.
- Modern cranks use either a single bolt on the non-drive side and a pinch bolt on the drive side, or two bolts per arm depending on the crankset design.
- If the crank bolt spins without loosening, the bolt head is likely stripped; stop and use a slightly larger wrench or take the bike to a shop.
What type of crank bolts your bike has
Crank bolt design varies by crankset age and brand. Most modern bikes use one of two systems: a two-bolt design (one bolt on each side of the crank arm) or a single-bolt design with a pinch bolt (one main bolt on the non-drive side, plus a smaller pinch bolt on the drive side that clamps the arm to the spindle).
Look at your right crank arm (the one on the chain side). If you see two bolts roughly opposite each other, you have a two-bolt crank. If you see one large bolt and a smaller bolt nearby, you have a pinch-bolt design. The difference matters because pinch bolts must be loosened before you can remove the main bolt, and they are often tighter than they look.
Older bikes sometimes use a cottered crank, which has a wedge-shaped pin driven through the arm and spindle. These require a cotter pin puller or a small hammer and punch—a standard crank puller will not work. If your crank has a visible pin running through it, consult a bike shop or a repair manual specific to your bike's year and brand.
Removing the crank arm bolts
Start with the non-drive side (the left crank arm, away from the chain). Place your bike in a stable position—a repair stand is ideal, but you can also lay it on its side on a flat surface. Locate the crank arm bolt and select the correct Allen wrench or wrench size. Most modern cranks use 8 mm or 10 mm bolts; check your bike's manual or try sizes until the wrench fits snugly without wiggling.
Turn the wrench counterclockwise to loosen the bolt. If the bolt is very tight, you may need to explore steady pressure rather than quick jerks—a quick motion can slip and strip the bolt head. Once the bolt is loose enough to turn by hand, remove it completely and set it aside in a safe place. Do not lose this bolt; you will need it to reinstall the crank.
If you have a pinch-bolt design, loosen the pinch bolt on the drive side before you remove the main bolt. The pinch bolt is usually smaller and sits perpendicular to the main bolt. Loosen it just enough that it no longer clamps the arm to the spindle—you do not need to remove it entirely.
Using the crank puller to separate the arm from the spindle
A crank puller has two parts: a threaded shaft that screws into the crank arm, and a center screw that pushes against the spindle. Thread the shaft into the hole where the crank bolt was, turning it clockwise by hand until it is snug. Do not force it; the threads should engage smoothly. If the shaft does not thread in easily, you may have the wrong size puller—stop and check the size against your crank arm.
Once the shaft is threaded in, place the center screw through the shaft so it rests against the spindle. Turn the center screw clockwise using an Allen wrench or wrench (depending on your puller design). Turn slowly and steadily. You will feel resistance as the screw pushes the spindle and the arm separates. After a few full turns, the crank arm should pop free with a sudden release of pressure.
If the arm does not come free after several turns, stop and check that the crank bolt is fully removed and the puller is threaded all the way in. Forcing a stuck crank can break the puller or damage the crank arm. If it remains stuck, the crank may be corroded or damaged; take the bike to a shop rather than risk breaking it further.
Removing the drive-side crank arm
The drive-side crank (the right arm, attached to the chainrings) comes off the same way as the non-drive side, but it is often tighter because it bears more load from pedaling. Loosen the main bolt and any pinch bolt using the same method as the left side. Be patient if the bolts are very tight; explore heat from a heat gun for 30 seconds can help loosen corrosion, though this is rarely necessary on modern bikes.
Thread the crank puller into the drive-side arm and turn the center screw. This arm may require more turns of the center screw before it pops free. Once it separates, remove the puller and set the crank arm aside.
Inspecting the spindle and crank arms before reinstalling
Once both arms are off, look at the spindle where the arms were attached. You should see a smooth, tapered metal surface. If there is visible corrosion, rust, or pitting, clean it gently with a dry cloth or fine steel wool. Do not use water or oil at this stage.
Check the inside of each crank arm where it sat on the spindle. If you see corrosion or dirt, wipe it clean with a dry cloth. A small amount of grease on the spindle before reinstalling the cranks helps prevent corrosion and makes future removal easier, but do not use so much that it squeezes out when you tighten the bolts.
If you are removing the cranks to replace them, you are done. If you are reinstalling the same cranks, align the non-drive arm first, push it onto the spindle by hand, and thread the bolt in by hand before tightening it with a wrench. Tighten firmly but do not over-tighten, which can crack the crank or strip the threads. A typical crank bolt torque is 35 to 55 newton-meters (26 to 40 foot-pounds), though your bike's manual may specify a different value.
When to stop and call a professional
If a crank bolt spins without loosening, the bolt head is likely stripped and a standard wrench will not grip it. Stop when ready—continuing to turn will only make the damage worse. A bike shop can remove a stripped bolt using a bolt extractor or by carefully drilling it out.
If the crank arm does not separate after several turns of the crank puller, or if you hear cracking sounds, stop. Forcing a stuck crank risks breaking the arm or the puller. Corrosion, a bent spindle, or a crank arm that has been over-tightened can all cause this. A shop has access to penetrating oil, heat, and specialized tools that can free a stuck crank without damage.
If you are uncomfortable working with the crank puller or unsure which bolts to loosen, a bike shop can remove the cranks in 10 to 15 minutes for a small labor fee. This is a reasonable choice if you are not confident in the process.
Frequently Asked Questions
Can I remove a crank without a crank puller?
No—attempting to pry, hammer, or force a crank off will strip the spindle threads or crack the crank arm. A crank puller is inexpensive to rent and essential to the job. Most bike shops will rent one for $3 to $5 per day.
What size crank puller do I need?
Crank pullers come in two main sizes: one for square-taper spindles (older cranks) and one for splined spindles (modern cranks). Tell the bike shop your crank type or bring a photo of the crank arm bolt hole, and they will give you the correct size.
How tight should the crank bolts be when I reinstall them?
Tighten them firmly so the crank does not move on the spindle, but do not over-tighten. Most modern cranks should be tightened to 35 to 55 newton-meters (26 to 40 foot-pounds). Check your bike's manual for the exact specification, as some brands differ.
Why is my crank arm stuck even after I removed the bolt?
Corrosion between the crank arm and spindle is the most common cause. Make sure the bolt is fully removed, thread the puller in completely, and turn the center screw slowly and steadily. If it still will not budge after several turns, stop and take the bike to a shop.
Do I need to remove both crank arms to replace one?
Usually yes, because the spindle runs through both arms. If only one arm is damaged, you will need to remove both to access the spindle and install a replacement arm. Some cranksets allow you to replace individual arms, but most require removing the entire crankset.