# Brakes

## The Science of Stopping: It's All About Friction - Bicycle Brakes Convert Kinetic Energy (Motion) Into Thermal Energy (Heat).

### Braking Distance

The approximate braking distance can be found by determining the work required to dissipate the bike’s kinetic energy:

Through the Work-Energy Principle it can then be said that:

$\left(\mu ×\mathrm{mass}×\mathrm{gravity}\right)×\mathrm{distance}=\frac{1}{2}×\mathrm{mass}×{\mathrm{velocity}}^{2}$

Finally, by rearranging the equation and cancelling like terms we can form an equation for braking distance:

$\mathrm{distance}=\frac{{\mathrm{velocity}}^{2}}{\left(2×\mu ×\mathrm{gravity}\right)}$

μ = coefficient of friction

### Rim Brake

• How's it Work? Rubber pads are pressed against the rim of the wheel.
• Advantages: inexpensive, lightweight, easy to maintain, mechanically simple
• Disadvantages: easily contaminated, less braking power

### Disc Brake

• How's it Work? Metallic or ceramic pads are pressed against a metal rotor that's attached to the wheel.
• Advantages: powerful, protected from contaminates, better heat dissipation
• Disadvantages: expensive, heavy, difficult to maintain