Bottom Brackets (BBs)
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.
This section 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.
