Originally Posted by
George
I now have a Shimano with 68 mm OB cups on my Spec, but when I had my Look with 68 mm OB cups, with a Sram BB, the Sram freewheeled much easier than the Shimano. Meaning if I backed pedaled, or spun the crank backwards on the Sram, it would spin like I had no chain on it.
George,
When putting that out there, you really need to be more specific as to what the comparison is.
Two things of relevance:
1. The preload which is adjustable on your Shimano crank can affect ability to free spin as you mention.
2. BB bearing seals affect ability for a crank to free spin. Even viscosity of grease affects this. Both have very little influence on overall crank performance or robbing of any wattage the rider may expend to propel the bicycle.
FYI