Do You Need A Brake Inspection or New Brake Pads?

Do You Need A Brake Inspection or New Brake Pads?
How do You Know?

Brakes turn the energy of motion into heat.  In other words, when you want to stop the friction between the brake materials, and the brake rotors/drums (more on this later) creates heat.  The faster you go the more heat the brakes create for you to stop.

 

There are two types of brake systems, shoes and pads.  Shoes are the old system, and they are rapidly being replaced with pads.  Many years ago the government mandated that all cars have front brake pads.  Most of the cars I work on have  4 wheel brake pads. 

Brake shoes:
When you press the brake pedal you push brake fluid from the master cylinder through the brake lines into the wheel cylinders.  The pressure of the fluid in the wheel cylinders pushes two plungers outward which force the brake shoes to make contact with the inside of the brake drum.  The pressure/friction of the shoes on the drum causes your car to stop.   One of the biggest problems with this system is that the shoes don’t always make 100% contact with the brake drum.  When you stop braking springs retract the shoes and remove them from touching the brake drum.  

Brake Drums:

These rarely need replacing.  The brake shoes rub on the inside of the brake drum.  When the brakes are inspected, we measure the inside diameter of the drum.  If the diameter is too large (there is a federal limit which is different for every model) then we need to replace the drum.  If the drum is not round, you will feel the brake pedal pulsate, and we need to resurface the brake drum.  If the inside surface is flat, we do not need to resurface it when re replace the brake shoes.

Brake Pads:

When you brake you push brake fluid from the brake master cylinder through brake lines into the caliper.  In the caliper, the brake fluid pushes a piston outward forcing the ‘inside’ brake pad onto the rotor.  This is a litter difficult to explain, so please bear with me… “For every force there is an equal and opposite force.”  When the brake pad pushes against the rotor, the caliper is forced back, causing the ‘outside’ brake pad to make contact with the outside surface of the brake rotor.  This is called a sliding caliper.  Ideally, both pads exert the same force on the brake rotor.   A few manufacturers don’t use sliding calipers.  These manufacturers use a brake caliper with pistons on the inside and on the outside of the brake rotor.

This post originally appeared here: http://autorepairchicago.blogspot.com/2012/05/how-do-i-know-if-i-need-brake.html 

You can read more about car repair here:  http://mastermindofdenver.blogspot.com/