Disc brakes are not "self-energizing" like drum brakes, so they require more pedal effort to apply. It's the magic of power brakes that allows a 98-lb. little old lady to bring two tons of a you name it luxury sedan to a screeching halt with little more than a light caress of her foot against the brake pedal.

Power brakes are great when they work correctly, but what happens when they don't? Suddenly it takes a lot more effort to bring the vehicle to a halt. This may increase the distance it takes to stop the vehicle and create a potentially dangerous situation. So if a vehicle is suffering from increased pedal effort, the first thing you should check is the power brake system.

VACUUM BOOSTERS
Most power brake systems use a vacuum booster to assist braking. Vacuum is good for a lot of things, like sucking gas through a carburetor, opening and closing airflow doors in a vehicle's climate control system, and for providing extra muscle for braking. But to assist braking, it takes a lot of vacuum.

How can something take a lot of nothing? After all, vacuum is the absence of atmospheric pressure. The answer is the higher the vacuum, the greater the atmospheric push to fill the void. As some famous scientist once said, "Nature abhors a vacuum." What he meant was as soon as you create a hole in the air (vacuum), the surrounding air tries to rush right in to fill it back up. So the "push" that a vacuum brake booster gives t...