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Brake Pads vs Rotors

At the service center we look at a machine as complex as an automobile, no mechanical component can be considered less vital than any other. Sure, a car or truck will continue to run with a hole in its exhaust, or with a sound system that doesn’t tune accurately, but all the machinery must be maintained in tip-top working order. If the steering goes out, a brand new starter motor won’t help; yet, if that starter motor fails, no amount of money invested in the fuel injection system will get the car going.

All that said, perhaps the most frightening experience for a driver is the loss of braking ability. Maintaining the components that comprise this equipment at their optimum must be a priority for all vehicle owners, and a working knowledge of how brakes function makes that maintenance easier to understand. At its most basic, the system is not complicated or difficult to fathom.

The Basic Concept

Ultra-modern, high-end vehicles are now coming on to the market with electronically controlled braking–effectively brake-by-wire braking systems. The technology debuted in North America with 2005‘s Lexus RX 400h SUV launch and, while this may well be the way of the future, at time of writing, most vehicles on the road still use a hydraulically-operated braking system. Ignoring bolt-on improvements and computerized safety devices (anti-lock braking, electronic brakeforce distribution and the like), the basic concept is as follows:

  1. The driver depresses the brake pedal, which increases pressure on the hydraulic fluid in the braking system’s pipes and components.
  2. That increased pressure is transferred, effectively immediately, throughout the entire system.
  3. The increased pressure is “looking for” a way to release the energy it now stores; it needs something it can force outward to compensate for the pedal being pressed inward.
  4. The entire braking system is static, made of pipes that cannot expand, and components that cannot move,except for the pistons which act within the braking components on the wheels themselves.
  5. The hydraulic fluid thus forces the pistons outward, which, in turn, pushes a static component (the brake pad), onto a rotating component (the rotor, also called the disc).
  6. The pads drag on the rotor, slowing it down.
  7. Rotors are attached to wheels, which therefore slow, too; the vehicle does the same.

This is, in simple terms, why a car slows gently when gentle pedal pressure is applied, yet screeches to a halt when a driver stamps downward in an emergency situation.

Other Technology

Pads Vs RotorsThe pressure applied to the brake pedal is increased within the hydraulic fluid by an arrangement called the master and slave cylinder assembly–or, in some designs, by a brake booster. This is properly called “hydraulic force multiplication.” Most traditionally-braked vehicles are fitted with one or the other, but the breakdown above still describes the fundamental principles.

The adversarial boxing match or wrestling bout, nature of the term “versus” isn’t misplaced here. The relationship between the two is extremely aggressive under harsh conditions, with the friction applied between pads and rotors, creating sufficient heat to set accumulations of brake dust on fire, and with the friction between the tires and the road being sufficient to peel rubber away.

What’s important to understand is that pads clamp down on rotors, and slowing the rotors slows the wheels proportionately.

No matter what make of vehicle you drive, the certified technicians at Norm Reeves Toyota San Diego can help you ensure your braking system is working at its optimum. The dealership is located at 5910 Mission Gorge Road, San Diego, CA 92120, where you’ll also find a full inventory of all new Toyota vehicles.