Originally Posted by
cyccommute
The larger diameter hollow spindle on external bottom bracket cranks is noticeably stiffer and lighter than square taper bottom brackets. However, the real advantage of external bottom bracket cranks is their ease of installation and maintenance. It takes only a couple of tools to install or remove a Shimano external BB crank. A 5 mm allen is all that is needed to tighten the arms onto the spindle or to remove it. If you have to replace the bearings...not something that happens any more often than replacing an internal BB...you could remove the BB with a pair of pliers.
To do the same operations with a internal BB requires 4 or 5 heavy tools. For touring, the external BB just makes sense.
I understand how they work, I have them on a couple of my bikes.
If you need a new BB while on tour you will be visiting a bike shop, no need to carry BB tools.
They are lighter but not so much as to be a must have.
I would have liked it if they were a significant improvement over square taper or splined but it just doesn't seem that way to me.