somervillebikes
Efficiency of Shimano IGHs
Figures and legends taken from Bicycle Quarterly, Autumn 2010
Interesting graph provided by Shimano regarding the mechanical efficiencies of two of their 8-speed IGHs. This may explain why in some speeds, the hub feels "sluggish" or harder to pedal than in another gear. Note the huge increase in efficiency when switching from 4th to 5th. This is much more pronounced in their lower end hub than in their higher end model.
However, from the perspective of a scientist who generates and scrutinizes such graphs daily, this graph, while interesting, is largely meaningless due to the unit-less y-axis. Are we supposed to be looking at percent efficiency? What is the axis range? If the y-axis in fact represents percent efficiency and the axis range spans 0-100% (for example), then the graph indicates a very pronounced effect from a practical standpoint (i.e., ~35% efficiency in 4th gear, and ~95% efficiency in 5th gear). But if, hypothetically, the axis range represents a narrow efficiency range--say 40-50%--then the peaks and valleys are largely insignificant in the real world (representing about 43% efficiency in 4th compared with 49% efficiency in 5th). Take-home message: be careful how you interpret this data!
Efficiency of Shimano IGHs
Figures and legends taken from Bicycle Quarterly, Autumn 2010
Interesting graph provided by Shimano regarding the mechanical efficiencies of two of their 8-speed IGHs. This may explain why in some speeds, the hub feels "sluggish" or harder to pedal than in another gear. Note the huge increase in efficiency when switching from 4th to 5th. This is much more pronounced in their lower end hub than in their higher end model.
However, from the perspective of a scientist who generates and scrutinizes such graphs daily, this graph, while interesting, is largely meaningless due to the unit-less y-axis. Are we supposed to be looking at percent efficiency? What is the axis range? If the y-axis in fact represents percent efficiency and the axis range spans 0-100% (for example), then the graph indicates a very pronounced effect from a practical standpoint (i.e., ~35% efficiency in 4th gear, and ~95% efficiency in 5th gear). But if, hypothetically, the axis range represents a narrow efficiency range--say 40-50%--then the peaks and valleys are largely insignificant in the real world (representing about 43% efficiency in 4th compared with 49% efficiency in 5th). Take-home message: be careful how you interpret this data!