Source: Wikipedia Commons

Here's a list of symptoms that can let you know it may be time to do a brake job:

• Longer stopping distances
• Pedal feels soft or spongy underfoot
• Brake light or ABS light comes on while braking
• Low brake fluid, which could be a sign there is a leak somewhere, or that your brake pads have worn down
• Vehicle pulls to one side or the other while braking, and is hard to control
• Pulsation or shudder through the brake pedal while braking
• Tendency for one or more wheels to lock up and skid while braking
• Excessive brake pedal travel, with the pedal going almost to the floor before brakes engage
• Pulsation or shudder through the steering wheel while braking
• Squealing, groaning, or metallic grinding noise while braking

Of these, the metal-to-metal grinding noise is by far the worst. It means the friction material of your brake pads has worn to a point where the rivets that hold them to the steel backing plate are exposed. Your only braking ability comes from metal-to-metal contact, and the rivets are quickly digging deep grooves into the rotors. We recommend replacing rotors with pads for several reasons anyway, but in this situation replacing rotors is an absolute necessity. But even more importantly, you're driving a very dangerous vehicle.

Depending on your vehicle and driving style, brake pads will generally last 40,000-60,000 miles. As a general rule, it's a good idea to have your brake pads inspected about once a quarter. If you see they're thinner than about 1/4", it's time for a brake job.