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Parts and tools for changing a bottom bracket
How difficult is it, and what tools are needed, to change out a bottom bracket?

Hi Dave,
There are 3 common bottom brackets shown here:
Which one do you have?

I have to go look at the bike when I get home. It's a fairly new specialized tarmac, and suspect it is the cartridge type set up. I sure appreciate your assistance!

To remove your crank arms you'll need this tool:
To remove the bottom bracket you'll need this:
Once removed, you'll have to replace the entire bottom bracket. Unlike traditional bearing/cup units, the cartridge BBs are sealed, and meant to be replaced rather than serviced. Any good bike shop can match up your old BB and sell you a replacement. I'm hoping to do a video tutorial on this soon. Let me know how it works out for you.

Thank you! What a great resource!

Hi Alex. I'm replacing a sealed bottom bracket also. Do you know what the torque specs would be on a Shimano UN54? There's nothing in the box telling me how tight to install it.

Tighten it with about 360 inch pounds, which equates to 30 foot pounds, or 40 Newton Meters (Nm).

Thanks Alex. Both sides? The left side is a plastic piece.

Sorry... yes only the metal end. The plastic side just needs to be snug.

Excellent. Thanks very much.

Hi there

Can I revive this thread please - apols!

I ask, as there appears to be two different tools required to remove both cups of a standard Shimano cartridge bottom bracket....

I've just picked up an old Orange Prestige which I'm about to restore, and I was able to remove the non-drive side (I believe the bb had been installed back to front) using a Shimano UN74 tool and a 32mm spanner. However, there is a plastic cup left in the bb in the drive side, and the same UN74 tool is too big to fit into the splines on this cup - what model of Shimano tool do I need to remove the cup that remains?

It was a cheapo CS-21 sealed cart bottom bracket for identification.
It should be the same tool for each side.

Am I correct that you've removed the cartridge and now just have the old plastic cup stuck in the frame?

As it's a plastic part, you coould probably cut it and break it to get it out.

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