Old 03-27-18, 02:07 PM
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Originally Posted by dabac View Post
The older, presumably higher quality units have a circlip that pull the brake shoes inwards, out of engagement. These tend to have - at most - a very marginal extra drag compared to other hubs.
But I've also seen a few newer/cheaper hubs w/o that circlip. In these, the brake shoes stay in engagement - but not under pressure - even when coasting, resulting in noticeable drag.

On the Shimano CB-E-110, I see the clutch cone unit (#9) has a spring inside. Its purpose appears to be to push the clutch away to disengage the brake shoes. If one brake shoe is installed on top and other on bottom, then the top brake shoe will fall down and rest on the clutch unit, without any drag. But the other shoe would fall and rest on the housing, which would drag.
In this case...I would hypothesize that the drag would be negligiable relatively to drag on the tire and drivetrain, if the brake is kept properly lubricated with fresh thin grease.

To test this hypothesizes scientifically...on a recent ride, both my buddy and I coasted together down this long overpass. Her 8-spd Cassette Shimano...mine KT coaster brake hub. We were similar weight and size. We started at the top together, and we arrived at the bottom together.
This test showed convincingly the coaster hub brake drag is negliable.

Last edited by mtb_addict; 03-27-18 at 03:27 PM.
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