An Overview Of Bottom Brackets

The humble Bottom Bracket, often known as a BB – sits within the Bottom Bracket shell on the frame. This acts – together with the bearings, as an axle system, helping the cranks rotate smoothly and efficiently.

There are a huge variety of Bottom Brackets on the market, and in your cycle mechanic practice you may come across anything from a very ancient piece, to an integrated top end BB unit costing several hundred pounds.

Subsequent articles will take you through the general theory and practice of Bottom Brackets: from adjusting to refurbishing, to replacing the most common types.

As always, and especially with the more modern components, it is useful to read the manufacturer guidelines also.

Initial Assessment

Identifying the type of Bottom Bracket is vital in ensuring that you make the right assessment before proceeding with any work. The following are the main different types you will encounter:

1. Open /Loose Bearing

2. Sealed/inboard

3. Outboard

4. BB30 and BB90

Common BB problems are finding them to be too loose, grinding or too tight.


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