For over 100 years, bicycles have had a chain ring fixed to the right hand crank as part of their drive train. The External Disk Brake (EDB) standard employs the same proven strategy but with an ingenious difference: the chain ring is replaced by a disc brake rotor, and the derailleur by a disc brake caliper. This innovation provides the smooth and secure stopping power of a disc brake for unicycles.
Mounting the rotor on the crank permits a wider flange spacing on the hub. This results in a stronger wheel at minimum weight, with no change in hub width.
The disc rotor mount add just 2 grams to the right hand crank, and no weight to the hub.
Works with a standard width hub for every wheel size from 24” to 36”, using a standard hydraulic bicycle disc brake and rotor.
The EDB was tested for both on- and off-road unicycling. It simply reverses the purpose of the front chain ring on a bike, which has already been proven on billions of bicycles over more than a century.
Kris Holm Unicycles offers EDB compatible Spirit double-hole cranks in several different lengths. Click for details.
No. The rotor is in the same location as a bicycle front chain ring. A 160 mm or 180 mm disc brake rotor is also smaller than most front chain rings. We recommend that shoelaces and loose pant legs be tucked away regardless of whether a disc brake is used on a unicycle.
It's rare but damage can happen. The EDB rotor is similarly vulnerable to ground impact than hub-mount disc rotors on bikes or unicycles. However, disc rotors are widely available and inexpensive to replace. KH frames are also rim brake compatible if this proves to be an issue.
Mostly, yes. The EDB standard works with hydraulic disc brakes containing International Standard (IS) mounts or IS adaptors. Mechanical disk brakes may not be compatible due to the larger size of caliper.
Potentially, yes. The EDB standard requires an IS brake mount on the right fork blade or bearing housing, 20 mm or narrower bearing housings (to ensure clearance of disc rotor bolts), and a standard unicycle hub with 154 mm or longer axle. A Nimbus brand D'brake disc mount works with Spirit cranks on many unicycles. Older (pre-2012) KH frames contain 22 mm wide bearing housings, and will likely require filing the bearing housing to prevent the disc rotor bolts from rubbing on the frame. User frame modifications void the KH warranty.
Yes and no. The current KH/Schlumpf hub mounts the cranks very close to the frame and does not contain a spacer between the crank and bearing. As such, most users find that the disc rotor bolts hit the frame when installed, even with KH frames. Many users have made modifications to successfully allow EDB use with the KH/Schlumpf hub (e.g. grinding the outside face of the bearing housing). However, frame modifications require some work, and void the KH warranty. Click here for additional notices regarding use of the KH/Schlumpf hub with disc brakes. This issue is currently being worked on and, of course, KH Spirit cranks are a high performance choice for the KH/Schlumpf hub regardless of disc brake usage.