Motorcycle Brakes - Part 3
Mechanical brakes operate by means of levers, pivots. adjusters. cables. springs, and cams. Each of these items plays an important role in stopping your motorcycle. It is a good idea to familiarize yourself with the parts in this system and how they operate as the proper maintenance and functioning of these systems can make the difference between a pleasant Sunday afternoon ride and a ride in an ambulance.
Levers, Pivots, and Adjusters
A lever assembly helps the operator gain mechanical advantage over the braking or clutching system of a bike. About a 6-to-1 mechanical advantage is gained at the lever. It is important to keep the pivot lubricated to ease operation. The adjustor simply provides a quick, easy way to compensate for stretch that develops in the cable over time.
The cable is basically a steel wire inside of a flexible rubber covered steel tube. It provides a flexible coupling between the operator and the brake. If the outer tube is held stationary at the ends, motion can be transmitted via the inner cable even if both have to go around corners and be flexing while the inner cable works.
The cable is attached to a brake lever that is splined to the brake activating cam. Once again, mechanical advantage of about 6-to-l is gained between the lever and the cam.
Strong retracting springs are connected between the brake shoes to return the brakes to a disengaged position. Lighter springs are used to return the levers and pedals to their ready positions.
Just as levers can be used to increase mechanical advantage, a hydraulic system can accomplish the same task. A force applied to a small piston in a hydraulic system over a long distance can be converted to a much stronger force over a short distance. This increase in force takes place when the original force from a smaller piston is applied through a liquid medium to a larger piston.
A motorcycle braking system uses this principle to increase hand pressure on a lever to the great energy required to clamp two pads together on a disc to stop the machine. To accomplish this, the hydraulic brake system uses a master cylinder, brake line, and a slave cylinder in the caliper assembly.
The master cylinder is the central unit in which hydraulic pressure is developed. Pressure from the rider's hand on the lever is transmitted to the master cylinder piston. As this piston is forced forward in the master cylinder, it pushes brake fluid ahead of it. Since the brake line and caliper piston are filled with fluid, the piston is acting upon a column of fluid. As hand-lever pressure increases, pressure on the caliper piston increases the pressure of the pads against the disc. These pressures build up throughout the system and result in quicker stopping.
Again, hydraulic brakes are the current standard as they are modern, efficient, and reliable... and are truly the only type of braking system that belongs on a modern motorcycle. Don't bet your life on anything less.