Drive Train

What is The Bottom Bracket on a Bike?

By: Alex Bristol

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The bottom bracket is a device that connects the cranks to the bike. This means that the cranks can rotate freely when pedaling. It also adds power to the drive train. The spindle and the shell depend on the width of the bottom bracket.

What you need to know is that when the bottom bracket is in good condition, you will be able to pedal smoothly without any resistance. This means that your energy you use on the pedals will be directed to the bike. You will find that bike bottom brackets are available in different designs that make them suitable for different types of bikes. However, the two common designs which you can find in modern bikes are threaded bottom brackets, square tapper bottom brackets and press fit bottom brackets.

Threaded bottom brackets

Threaded bottom brackets only works with frames which uses a threaded bottom bracket shell. This means that they should be screwed on the frame. You should also note that they are usually joined together within cups. What you need to know is that threaded bottom brackets are not equal which means that you cannot use them with other types.

The most common types of threaded bottom brackets are English and Italian. The two sides of the Italian brackets are usually threaded. On the other hand, English threaded brackets usually have opposite threading just like the pedals. The major advantage of English threaded brackets is that the drive side does not become loose when pedaling. In general, threaded bottom brackets are very easy to install and also to maintain.

Press Fit Bottom Bracket

These ones are also referred to as threadless bottom brackets. They are usually press into the frame bottom bracket shell. They also feature cartridge bearings which are pushed into the shell. Their design provides thick crank spindles. As a result, they are very stiff and efficient.

Square tapper bottom brackets

These ones are very common and they usually combine the crank’s axle and the bearings together into one removable part. The cranks are attached on two square tapers on both sides of the bottom bracket. Square taper bottom brackets are very common on older vintage bikes.

Disadvantages of bottom brackets

In case the bottom bracket is not adjusted properly, it may wobble or develop play and as a result, it will lead to poor energy transfer from you to the bike. Another problem is that in case the bearings get contaminated with water or dirt, they may wear out since there will be more friction when turning the ranks. This means that you will also need to apply some energy when pedaling.

How to maintain Bike bottom brackets

If you are using a threaded bottom bracket, you should remove it frequently and refresh the anti-seize compound which prevents it from getting stuck in the frame.

Irrespective of the type of bracket you are using, always remember to check the bearings. Again, you should clan the bike frequently to prolong the lifespan of the bracket.  Since there are different types of bottom brackets, you will need different tools during installation. However, you can take the bike to a bike shop in case you have problems when installing or removing a bottom bracket.


1.What is a bottom bracket – Post by bike radar

2.Road bike bottom bracket standards – Post by cycling weekly

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