Patent ID: 7178646

Claim:
A symmetric master cylinder for a bicycle hydraulic disc brake comprising: a bar clamp attached to a master cylinder housing for attaching the master cylinder housing to a bicycle handlebar along a longitudinal clamp axis; a cylinder wall associated with the master cylinder housing, the cylinder wall comprising a cylinder interior and a cylinder exterior extending axially of a cylinder axis, the cylinder having a first end and a second end; a reservoir for hydraulic fluid comprising a first wall comprising only a limited radial portion of the cylinder exterior and an elastomeric diaphragm, wherein the cylinder axis and the longitudinal clamp axis lie in a plane substantially symmetrically bisecting the first wall; a port between the first and second cylinder ends in the first wall providing fluid communication between the reservoir and the cylinder interior; and a piston within the cylinder having a seal operatively associated therewith, the piston being moveable along the cylinder axis between the first and second cylinder ends, the seal preventing flow of hydraulic fluid from the reservoir to the second cylinder end upon the seal advancing axially past the port as the piston moves from the first toward the second cylinder end; wherein the reservoir is located substantially entirely between the longitudinal clamp axis and the cylinder axis.