Check cranks and the bottom bracket

A creak or knock every time you pedal often comes from the cranks, pedals or bottom bracket. Some of these checks are easy at home. Others, especially on a mid-drive e-bike, belong at a shop. This guide follows Park Tool's crank and drivetrain noise guides, Shimano's care advice and Bosch's drive unit manual.

What you need

• Hex keys and a torque wrench
• A crank puller that fits your crank, if you remove an arm
• A bottom bracket tool for your bottom bracket, if you go that far
• Bike grease

Know your crank type

• Square taper. The arm wedges onto a tapered square spindle. Park Tool says enough bolt torque usually stops these from creaking (Park Tool). Rad's RadWagon 5 manual lists a crank puller for its square taper bottom bracket (Rad RadWagon 5 manual).
• Splined. Shimano Octalink uses 8 splines and ISIS Drive uses 10, and the two don't swap (Park Tool).
• Mid-drive motor. On a Bosch, Shimano or similar mid-drive, the crank arms fit the motor's spindle and there is no separate bottom bracket to service at home. Bosch says not to open the drive unit and to replace cranks and chainrings only with identical or approved parts (Bosch).

Steps

1. Turn the bike off and remove the battery.
2. Find when it creaks. Park Tool suggests short test rides, noting when the noise happens. A creak once per crank turn points to the crank or pedal area. A noise every two or three turns points to the chain (Park Tool).
3. Check for play. Shimano says to test the bottom bracket, pedals, hubs and headset for roughness or play (Shimano). Hold one crank arm and push it in and out toward the frame. Any knock or movement needs a closer look.
4. Check the pedals. Park Tool says pedals should be tight in the cranks, typically 40 Nm (Park Tool). Rad lists 35 Nm for its pedals (Rad RadWagon 5 manual). See replace pedals.
5. Check the crank bolts. Park Tool's typical crank bolt value is 40 Nm and its crank guide gives 34 to 50 Nm depending on brand (Park Tool, Park Tool). Rad lists 35 Nm for the RadWagon 5 crank arm bolt (Rad RadWagon 5 manual). Use your bike's number.
6. Check the chainring bolts. Park Tool gives about 8 to 12 Nm for steel chainring bolts, with mild threadlocker or grease (Park Tool). Rad lists 10 Nm on the RadWagon 5 (Rad RadWagon 5 manual).
7. If a square taper arm still creaks at full torque, Park Tool says to remove it and grease the pressed surfaces under the bolt head and on the threads, but keep the square taper itself clean of grease (Park Tool). Use a crank puller threaded fully into the arm before you turn it, as Park Tool warns (Park Tool).
8. Threaded bottom brackets. Park Tool says to check that the cups or lockring are secure and tight to at least 35 Nm (Park Tool). Rad lists 60 Nm for the RadWagon 5 bottom bracket cups (Rad RadWagon 5 manual).

Common mistakes

• Riding a loose crank. Park Tool says if the spindle end no longer sits recessed in the crank hole, the bolt can't hold the arm tight and the crank needs replacing (Park Tool).
• Starting a crank puller with only a few threads in. It can strip the arm.
• Greasing a square taper. Grease goes on the bolt, not the taper.
• Treating a mid-drive like a normal bottom bracket. The motor isn't something to open.

Videos

When to get a pro

• Any play, grinding or noise from a mid-drive motor. Bosch says to have it serviced by an authorized dealer (Bosch).
• Press-fit bottom brackets. Shimano says these need special tools and suggests a shop (Shimano).
• A crank arm with damaged threads or a rounded taper.
• More: e-bike noises and when to call a pro.

Sources

• Three-Piece Crank Removal and Installation, Park Tool
• Troubleshooting a Noisy Drivetrain, Park Tool
• Spring cleaning and maintenance, Shimano
• Drive unit manual, Bosch eBike Systems
• RadWagon 5 owner's manual, Rad Power Bikes

Stuck after these checks? Find a shop near you.