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BOTTOM BRACKETS: What they are, what they do and how to remove and replace them

If you’ve never heard of a bottom bracket, don’t worry, a lot of people haven’t!


This is our quick guide to caring for one of the most important parts of your bicycle – the bottom bracket.

What is a bottom bracket?

A bottom bracket (BB) is a component with a bearing that is buried inside your frame. It’s used to connect the cranks to the rest of the bicycle, and allows them to rotate freely. No BB means no pedalling, as the cranks would be stuck in place without it!


Think of it as like an axle in a car.


There are a number of types of bottom brackets used in modern bicycles, and they all fall into the category of either ‘Threaded’ or ‘Press Fit.’ This refers to how they are installed into the bicycle – either ‘pressed’ into the frame or threaded. When servicing or buying a replacement bottom bracket, you need to be sure you know which one is compatible with your bicycle.

Wear and tear

Like all moving parts of your bicycle, your bottom bracket needs a little TLC every now and then and will require occasional replacement.


As the BB contains a bearing, if you fail to keep it well-maintained it will stop rotating as efficiently and will feel stiff and gritty as you pedal. So when your bottom bracket is dying, you need to push harder just to turn the pedals. Not ideal!


How fast your bottom bracket wears down is dependent on how often you ride and where you do it. If you rarely ride and only cycle on clean, dry roads, your BB could last years! But if you’re riding through wet mucky trails every day, all that mess will start to work into your bottom bracket’s bearing and wear it down.


Lucky for you all, removing a BB in order to clean it up or replace it is a relatively straightforward task, and we’ve got the tools for the job!

How to remove a Threaded bottom bracket
  1. Remove the cranks – this will require a heavy-gauge Allen Key, typically sized 8mm. The PRO BIKE TOOL Allen Key Set includes one of these. Simply loosen the non-drive side bolt and pull the cranks out of the frame.
  2. Insert the PRO BIKE TOOL BB Tool into the left ‘cup’ of the bottom bracket – i.e., the side away from your drivetrain. Turn the tool counterclockwise to remove the cup.
  3. Repeat the process but turn clockwise to remove the right-side cup. The BB is now free and ready to remove!
How to remove a Press Fit bottom bracket
  1. Remove the cranks per step 1 above.
    Remove the dust caps that cover the bearing seals from either side of the bottom bracket.
  2. Use a Press Fit BB removal tool (watch this space for a PRO BIKE TOOL product to help you with this!) to remove the first bearing by inserting the head of the tool into the bottom bracket. Push the tool all the way through the bottom bracket until you have a secure fit against the bearing at the side farthest away from you. Push the guide stopper of the tool to sit flush against the near side of the bicycle.
  3. With the head of the BB tool firmly secure against the far-side bearing, use a hammer to tap the handle of the tool and dislodge the component. Do this firmly but carefully and the bearing will slowly creep out.
  4. Repeat the process to remove the bearing from the other side.

Once you have cleaned up your old bottom bracket with a rag and cleaning agent or have a new one to replace it, it’s time to install it!

How to install a Threaded bottom bracket
  1. Ensure the bottom bracket shell is nice and clean to start, and then rub grease into all the threads using a finger or brush.
  2. Figure out which BB cup goes on which side of the bearing. The non-drive-side has a left-hand thread and the drive-side cup has a right-hand thread.
  3. Grease the first cup, insert it into the relevant side of the bottom bracket and finger-tighten it. Once the bearing is as tight as you can get it by hand, use either the PRO BIKE TOOL BB Tool or a bottom bracket spanner to tighten it further.
  4. Repeat the above process with the other bracket cup.
  5. Reinstall the cranks.
How to install a Press Fit bottom bracket
  1. Ensure the bottom bracket shell is nice and clean to start.
  2. Use a bearing cup press (watch this space for a PRO BIKE TOOL product to help you with this!) to ‘push’ the first bearing into the frame. Put the bearing onto the shaft of the tool and insert the tool into the bottom bracket shell. Rotate the handle of the tool to firmly but carefully press the bearing into the BB shell. One the bearing is secure, slide the tool out of the bicycle.
  3. Repeat the process on the other side to install the second bearing. This will require a little more muscle as you are both installing the bearing and connecting the two sides of the component together by pushing them into each other.
  4. Reinstall the cranks.

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