A bottom bracket – often known as a BB – sits within the BB shell on the frame and acts, together with the bearings, as an axle system, helping the cranks rotate smoothly and efficiently.
There are a huge variety of BBs 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 hundreds of 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. The following are the main different types you will encounter:
Common BB problems are finding them to be too loose, grinding or too tight.
