i have a set of the older I9s, coasting the drag is definitely noticable compared to my stans or bontrager hubs, but no it wont completely kill your ride.
I would love to try out a set of hydra hubs, and a set of onyx hubs (bc sprag clutch ?)
I would love to try out a set of hydra hubs, and a set of onyx hubs (bc sprag clutch ?)