The bulk of Danish bikemaker Coh & Co’s urban bikes are made of a layered composite of wood and carbon they call WOOCA. But the designers behind the brand got their start in more marine industry carbon and mixed composites. So it isn’t such a surprise to learn that their striking new belt-drive Carla commuter bike gets constructed of a unique mix of basalt stone fiber and more conventional carbon, to create a more robust lightweight bike ready to take life on city streets.
Coh & Co Carla basalt+carbon fiber prototype urban bike
The new Carla concept bike is being developed around a concept of creating a city bike more resilient than traditionally more fragile carbon fiber, while retaining much of the same strength, stiffness, and light weight characteristics. Coh & Co wanted to create a lightweight urban bike that could stand up to year-round city riding, with only minimal maintenance.
FIRM glass + basalt + carbon fiber composite tech
At the heart of the bike is a new fiber material tech called FIRM, that mikes together glass fibers, basalt fibers, carbon fibers, and a resin binder. Coh & Co says that this new composite material mix promises the lightness & stiffness of a regular carbon frame, yet is both more robust when it comes to impacts, and is easily repairable if it actually is damaged.
The mix of fibers are molded over a lightweight core (more like carbon wheels have been, rather than most recent carbon frames.) The result is a relatively light frame (not sure really what that means) that its makers say exhibits unusually good vibration damping. That makes for a comfortable ride on rough city streets, but also a tough bike that will last longer.
Carla composite urban commuter – Tech Details
The basalt+carbon composite frame is paired with a Gates belt drive setup to deliver light, efficient, no-maintenance power transfer. Of course a belt drive requires both a stiff rear end to keep the belt from jumping under flexing loads, but also requires a split or open rear end to thread the one-piece belt loop in. Apparently the FIRM material is ample stiff, as Coh & Co were able to build this working prototype bike with just one seatstay & one chainstay making it simple to install the belt.
A Shimano Alfine internally geared hub give easy to manage gearing range, with 8 & 11 speed options, and bolts securely onto the alloy dropouts that are in turn bolted to the composite frame.
Coh & Co tops Carla off with their own Esse saddle that is marine certified to survive whatever weather throws at it. And then for wheels it uses 650B eyeleted Gippiemme hard anodized alloy rims, again to survive rough urban life. Coh & Co also has a set of fiber glass mud guards in the works for Carla with maintenance free stainless steel stays.
For now the unique angular composite bike remains a pre-production prototype. But Coh & Co hope to have the Made in Denmark urban commuter Carla with her ‘heart of stone’ available soon.