How to Replace a Shimano Threaded Bottom Bracket


There are too common types of bottom brackets on modern bikes.

One is the press bit the other one is the threaded which is exactly what we've got on this bike. Here in this video we can show you how to remove and then replace a threaded bottom bracket.

The only thing that you need for this job:
A tool correctly fit onto the bottom bracket cups and probably a torque wrench if you want to do things correctly.

Of course you also going to need the correct tools to remove the crank set in order to get to the bottom bracket in the first place.

To remove our shimao Shimano Ulteg ra cranks first needed to undo the 5mm crank bolts, then remove the threaded end cap using a Shimano tool. Finally push the pin away away from the locator hole. You can then pull the non drive side crank away from the frame.

Next push the axel of the drive side through the bottom bracket, then coming around to the other side the bike remove the chain from the chainring pull the crankset away from the frame. We also got a more detailed video on removing cranks.

You now need a special bottom bracket tool that fits the outer circumference of the bearing cups. I'll place the tool on the cups and hold it tight and straight to loosen the cups in the frame.

Generally be pushed clock-wise on the right hand side anti-clockwise on the left. Many bottom brackets have directional arrows. You might need to push hard to get the cups moving initially.

After that they'll simply unscrew do the same on the other side and once you remove the bottom bracket give the frame threads a quick clean out. Then smear with light grease before refitting. Refitting is simply the reverse process there were any spaces behind the bottom bracket cups, make sure you put them back in the same place before you put it back on.

You can start threading and tightening the bottom bracket cups by hand then you need to use a special tool and the torque wrench. On our particular bottom bracket they recommend a torque 34 Nm. Once it's tightened and your ready to put you crank set back on wrap the chain around the bottom bracket shell then push the drive side axle through the bottom bracket, push the non drive side crank onto the axle perpendicular to the drive side crank. Push the safety pin back into the locator hole. Put the threaded end cap in on the non-drive side crank set. Finally, tighten the 5mm bolts back up on the crank, in this instance the recommended torque is 12 to 14 Nm.