The brake master cylinder is the heart of your braking system, pumping fluid at high pressure to all the wheel cylinders. Even if it's not leaking externally, a faulty internal bore may allow fluid past the seals causing a loss of efficiency and excessive pedal travel. Early Minors with 7" front drums used a 7/8" bore master cylinder CBS133. In 1964 the brake drum increased to 8" with a 13/16" master CBS144. Because changing the cylinder is job you don't want to do twice, we recommend replacing rather than rebuilding brake cylinders when possible. CBS144 now replaces the obsolete CBS133.