The external or outboard Bottom Bracket units that you will most commonly come across, will probably be made by Campagnolo, Shimano Hollow Tech II or SRAM. There are lots of different brands of external/outboard Bottom Bracket though, and if you are faced with another type in the workshop – it is best to follow the manufacturer instructions.
Campagnolo
The Campagnolo Ultra Torque system integrates both spindle and bearings into the arms. The cups are installed without bearings and there is also a “wavy” washer – used to account for variations in frame shell width, on the left side cup.
SRAM
The spindle is a permanent press fit into the drive side arm. No spacers are need or required and the left arm has a one key release system which requires no puller for removal.
Shimano Hollow Tech II/X type/Ultra Torque
The Hollow Tech II system is the first Bottom Bracket system in which the bearings are outside of the Bottom Bracket shell. Because of this, the bearings can be of a wider diameter and therefore the spindle is also wider. This makes the crankset stiff and the bearings less prone to wear and tear. It also means that the problem of Bottom Bracket cups getting stuck in frames is a thing of the past. The Bottom Bracket spindle in these units is attached to either the right hand crank, or both the right and left hand crank, and there are a variety of different joining methods to consider.
