Outside of an oil change, your vehicle's brakes, and brake replacement, are the most common maintenance issue you'll deal with during your car's lifetime. Knowing the warning signs of brake deterioration can mean getting them repaired well before they become a high cost problem or, worse, fail entirely, leaving you without a way to stop.
First, let's look at how the braking system on most vehicles works, what the warning signs are, and what repair and replacement requires. Most competent home mechanics can do a brake replacement with only simple tools and a little know-how, potentially saving hundreds of dollars. Even the mechanically inept, however, can minimize their brake replacement costs by catching the problem early. See our Brake Repair Cost article for information on costs associated with brake systems repair.
How the Braking System Works
The braking system on a typical vehicle has four basic components that work in concert.
The brake pedal (and emergency brake lever) signals the braking system to stop. It does so by compressing a chamber inside the brake master cylinder, typically located directly in front of the driver on the inside of the engine compartment and mounted to the firewall.
The master cylinder pushes fluid through the brake lines to match the amount of pressure the driver is applying to the pedal.
Calipers and shoes are pressed into a rotor or drum by the pressurized fluid from the master cylinder, creating friction that slows the vehicle.
From driver to master cylinder to brake calipers/shoes to rotor/drum, the system safely stops the vehicle. New technologies such as ABS and better pads/shoes have improved how vehicles slow and stop as well as added longevity to the maintenance intervals.
When pads or shoes press against rotors or drums (typically the rotors are at the front and the drums are on the rear of the vehicle), the friction causes the pads to slowly wear down with use. Eventually, they will require brake replacement.
Indications of Required Pad/Shoe Brake Replacement
The first indication of needed maintenance and brake replacement of pads and shoes is a general "softening" of the brake pedal. It becomes easier to push and takes more force to produce a slowing or stopping result. This is because more fluid pressure is needed to press the now-thin pads against the opposing surface of the rotor/drum in order to create the amount of friction needed to stop the vehicle.
Another indication is a slight squealing or grinding sound. Squealing is a better indicator as many pads and some shoes have built-in indicators that, when the pad reaches a certain point of thinning, scrape lightly against the rotor or drum and indicate that the pads require replacement.
It's imperative that as soon as you hear any strange noise coming from your wheels, you take the car to a mechanic for diagnosis.
If the squealing is ignored, eventually it will turn to a grinding sound as the base of the pad/shoe begins to grind directly against the rotor/drum (metal-to-metal contact). This is an extremely unsafe condition and will also become expensive to repair as the rotors or drums will almost surely need replacement as well ñ potentially tripling or quadrupling your brake repair cost.
A good mechanic, professional or not, is usually familiar with pad and shoe replacement. The procedure is fairly straight forward and can be done with simple hand tools.