Maintenance : changing a bottom bracket

30-12-22 | Simon

To change a bottom bracket on a bike, you will need the following tools:

1. A bottom bracket tool (a specific wrench or socket that fits the bottom bracket cups)

2. A crank arm extractor tool (a specific tool that is used to remove the crank arms from the bottom bracket spindle)

3. An adjustable wrench or a socket wrench

4. A rubber mallet (optional)

Here are the steps to change a bottom bracket on a bike:

Shift the bike chain onto the smallest cog on the rear derailleur and the middle or inner chainring on the front derailleur. This will give you more clearance to work on the bottom bracket.

Remove the crank arms from the bottom bracket spindle. Use the crank arm extractor tool to loosen and remove the crank arm bolts. Depending on your bike, you may also need to use an adjustable wrench or a socket wrench to loosen the bolts.

Once the crank arms are removed, use the bottom bracket tool to loosen and remove the bottom bracket cups from the frame. You may need to use an adjustable wrench or a socket wrench to hold the opposite side of the cup while you turn the bottom bracket tool.

If the bottom bracket cups are stuck, you may need to use a rubber mallet to gently tap the cups out of the frame. Be careful not to damage the frame or the cups.

Once the bottom bracket cups are removed, you can remove the old bottom bracket from the frame.

To install the new bottom bracket, start by placing it into the frame. Make sure that the bottom bracket is seated correctly in the frame and that the spindle is properly aligned.

Install the bottom bracket cups into the frame using the bottom bracket tool. Tighten the cups to the recommended torque (usually around 30-40 Nm).

Install the crank arms onto the bottom bracket spindle. Use the crank arm extractor tool to tighten the crank arm bolts to the recommended torque (usually around 40-50 Nm).

Test the bottom bracket by pedaling the bike and shifting through all of the gears. Make sure that the bottom bracket is tightened correctly and that there is no play or wobbling in the cranks.

That's it! You should now have a fully installed bottom bracket on your bike.