Nothing is more important than your car's ability to stop itself.
Even race car drivers will tell you that a car's braking capacity takes precedence over its acceleration. Putting a car through a wall is not nearly as much fun as touching the brakes slightly, banking into a turn, and scooting out the other side.
But braking systems often fail us, usually from our own neglect. In the case of braking, it's essential that we maintain optimum friction pad depth to insure maximum performance of the braking system. In layman's terms: change your brake pads!
There are two ways to determine whether the pads need replacing:
First, visually. If the pad depth is less than ¼ inch, plan on replacing it soon. If it's less than 1/8 inch, you're getting close to damaging the rotor, so do it ASAP. This varies slightly from car to car, but is a good general guideline.
Second, by ear. They build these little noisemaking shims into the brake assembly to tell you when the pads need changing. Are you hearing a screeching sound when you apply the brakes, like a mouse trying to escape? You're overdue for a reline. (If the sound is more a scrape-y metal rasp, you've already damaged your rotors and need to fix the brakes immediately.)
Remember the rule: BETTER TOO SOON THAN TOO LATE.
By Scott Memmer (Edmunds.com)