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A master cylinder assembly for a hydraulic bicycle braking system that includes a master cylinder having a first end and a second end, a first piston having a first end and a second end disposed in and movable within the master cylinder, a second piston disposed in and movable within the master cyli

A master cylinder assembly for a hydraulic bicycle braking system that includes a master cylinder having a first end and a second end, a first piston having a first end and a second end disposed in and movable within the master cylinder, a second piston disposed in and movable within the master cylinder, and a modulator configured to modulate a first pressure that is applied to the second end of the first piston.

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What is claimed is: 1. A master cylinder assembly for a hydraulic bicycle braking system comprising: a master cylinder having a first end and a second end; a first piston disposed in and movable within the master cylinder, wherein the first piston has a first end, a second end and an axially aligne

What is claimed is: 1. A master cylinder assembly for a hydraulic bicycle braking system comprising: a master cylinder having a first end and a second end; a first piston disposed in and movable within the master cylinder, wherein the first piston has a first end, a second end and an axially aligned through hole; a second piston disposed in and movable within the master cylinder, wherein the second piston includes a larger diameter portion and a smaller diameter portion having a distal end that extends through the hole in the first piston; a first fluid containing region at least partially defined by the second end of the first piston, the distal end of the smaller diameter portion of the second piston and the second end of the master cylinder, wherein the first fluid containing region includes an outlet that extends outside of the master cylinder, and wherein a first pressure is applied to the second end of the first piston by the fluid in the first fluid containing region; and a modulator configured to modulate the first pressure. 2. The master cylinder assembly for a hydraulic bicycle braking system of claim 1 further comprising a piston spring disposed between the distal end of the second piston and the second end of the master cylinder, wherein when the first pressure exceeds a pre-determined second pressure, the modulator modulates the volume of the first fluid containing region. 3. The master cylinder assembly for a hydraulic bicycle braking system of claim 2 wherein the modulation is caused by movement of the first piston relative to the second piston. 4. The master cylinder assembly for a hydraulic bicycle braking system of claim 2 further comprising a second fluid containing region defined between the first piston and the second piston, wherein the modulator also modulates the volume of the second fluid containing region. 5. The master cylinder assembly for a hydraulic bicycle braking system of claim 1 wherein the modulator is disposed between the first piston and the larger diameter portion of the second piston and is movable within the master cylinder. 6. The master cylinder assembly for a hydraulic bicycle braking system of claim 5 wherein the modulator comprises an elastic material. 7. The master cylinder assembly for a hydraulic bicycle braking system of claim 6 wherein the modulator comprises a spring, and wherein the spring biases the first piston away from the larger diameter portion of the second piston in an axial direction. 8. The master cylinder assembly for a hydraulic bicycle braking system of claim 6 wherein the modulator is comprised of rubber, and wherein one end of the modulator contacts the first end of first piston and other end of the modulator contacts the second piston. 9. A hydraulic brake lever assembly for a bicycle comprising; a housing adapted to be attached to a handle bar; a lever pivotably connected to the housing and having a range of travel comprising first and second regions; a master cylinder disposed in the housing and having a first end and a second end; a first piston disposed in and movable within the master cylinder, wherein the first piston has a first end, a second end and an axially aligned through hole, and wherein a first pressure is applied to the second end of the first piston; a second piston disposed in and movable within the master cylinder, wherein the second piston includes a larger diameter portion and a smaller diameter portion having a distal end that extends through the hole in the first piston, and wherein the second piston is operatively connected to the lever; a first fluid containing region at least partially defined by the second end of the first piston, the distal end of the smaller diameter portion of the second piston and the second end of the master cylinder, wherein the first fluid containing region includes an outlet that extends outside of the master cylinder; and a modulator disposed between the first piston and at least a portion of the second piston and movable within the master cylinder; wherein movement of the lever in the second region causes the modulator to modulate the first pressure. 10. The hydraulic brake lever assembly for a bicycle of claim 9 wherein movement of the lever in the second region causes the modulator to modulate the volume of the first fluid containing region. 11. The hydraulic brake lever assembly for a bicycle of claim 10 wherein the modulation is caused by movement of the first piston relative to the second piston. 12. The hydraulic brake lever assembly for a bicycle of claim 11 wherein the modulator comprises a spring, and wherein the spring biases the first piston away from second piston in the axial direction. 13. A master cylinder assembly for a hydraulic bicycle braking system comprising: a master cylinder having a first end and a second end; a first piston having a first end and a second end disposed in and movable within the master cylinder; a second piston disposed in and movable within the master cylinder, wherein the second piston includes a larger diameter portion and a smaller diameter portion, wherein the larger diameter portion has a first end and a second end and the smaller diameter portion has a distal end; a modulator movable within the master cylinder and disposed between the first end of the first piston and the second end of the larger diameter portion of the second piston; and a first fluid containing region at least partially defined by the second end of the first piston, the distal end of the smaller diameter portion of the second piston and the second end of the master cylinder, wherein the first fluid containing region includes an outlet that extends outside of the master cylinder, wherein the modulator modulates the distance between the first end of the first piston and the second end of the larger diameter portion of the second piston. 14. The master cylinder assembly for a hydraulic bicycle braking system of claim 13 wherein the first piston defines a through-hole, and wherein the smaller diameter portion of the second piston extends through the through-hole. 15. The master cylinder assembly for a hydraulic bicycle braking system of claim 14 further comprising a piston spring that biases the second piston away from the second end of the master cylinder. 16. The master cylinder assembly for a hydraulic bicycle braking system of claim 15 wherein the smaller diameter portion of the second piston includes a stopper on an end thereof, and wherein the piston spring is in contact with the stopper. 17. The master cylinder assembly for a hydraulic bicycle braking system of claim 16 wherein the stopper comprises at least one nut that is threaded on the end of the smaller diameter portion.