Bicycle brake system

A hydraulic brake system for a two wheel bike having a handlebar comprising:

• a master cylinder assembly mounted on the handlebar,
• said master cylinder assembly including:
• an outer housing,
• a tubular cartridge body mounted in the outer housing,
• a master piston mounted in the cartridge body,
• an operating lever pivotally mounted on the outer housing,
• a push rod operatively connecting the operating lever to the master piston,
• a spring mounted in the cartridge body to bias the master piston to an inoperative position in the cartridge body,
• a resilient bladder enclosing the cartridge body,
• a hydraulic fluid in said bladder,
• a port timing hole in said cartridge body operatively connecting the cartridge body to the bladder to maintain fluid in the cartridge body, a brake assembly mounted on a caliper housing and a brake line operatively connecting the cartridge body to the brake assembly.