Suntour XCD 6000 Roller-Cam Brake Caliper
Brand new Suntour XCD 6000 roller-cam brake caliper (a single caliper that will mount as either a front or rear brake). Recently discovered in Suntour's warehouse in Osaka Japan. They are still in sealed bags (no retail packaging)
These brakes were fitted to high end mountain bikes at the end of the 1980's early '90's and also to some tandems. They deliver very smooth and powerful braking. They are the ultimate development of cantilver style brakes.
This caliper will not mount on traditional mountain bike cantilever posts or studs the positioning of the posts on the forks/stays is different. However U-brake calipers mount similar to roller-cam brake calipers, so if your particular mountain bike or tandem will accept U-brakes, then this roller cam brake caliper should also mount fine.
The mechanics of a roller-cam brake caliper are superior to cantilever brakes. The way this works is the triangular shaped cam is pulled upward by the brake cable (as you squeeze the brake levers) and each side (edge) of the triangle contacts rollers at the top of each caliper arm. As the cam pushes these rollers outward (as the rollers slide down the edge of the triangle), the caliper arms pivot. The profile of the cam progressively controls the leverage throughout the pull of the lever.