With no details anywhere, other than a video posted on Vimeo, a French company called HXR is about to release a transmission for enduro riding. Designed as the opposite of current systems, the HXR fixes the cassette position to the rear hub so that it cannot freewheel, and then allows the chainrings on the crank to freewheel around the crank arm. It may sounds confusing, but its pretty simple, basically nothing changes about how you ride the bike, except the drivetrain never stops moving while the bike is moving.
This can possibly give some advantages such as being able to shift while coasting, so that you could drop a few gears while going through a corner, and come out strong. That seems to be the idea HXR is going after since they are aiming this product at the emerging Enduro market.
While the good idea is there, it is actually nothing new. Schwinn made a series of bikes in the 1970’s that did exactly the same thing. If you have ever ridden one of those bikes, you would know that it is actually kinda novel when it is working properly. But if it derails, chainsucks, or jams a shift, the bike can come to a very abrupt, skidding halt. This could be a huge concern for modern mountain bikes, where a chain lodged between the tire and carbon chainstay, yet being pulled by the full momentum of a moving bike could destroy a bike in seconds.
We will have to wait and see all the details when they fully release it in the near future. Jump past the break to see the drivetrain in action…
One of the benefits to the design could be less unsprung weight since the hub no longer needs the freehub mechanism. It looks like HXR might be taking that to the extreme with a machined hub shell with large lightening holes. Let’s hope the bearings have excellent seals.
As promised, the Schwinn freewheel crank from Youtube user micycle01. Freewheel cranks are also popular on trials bikes, though typically single speed.