Your brake pedal is the only thing that physically connects you to your brake system. Several different sensations can be felt through your brake pedal depending on the circumstances and the road surface. You can tell a great deal about the health of your braking system through these sensations. They may even tell you if an extremely important component is due for some work.
If your pedal sinks when you apply the brakes may mean something serious, especially if your pedal sinks when constant pressure is applied. It is normal for power brake systems to sink down a couple inches when the engine is first turned on, but the pedal should remain firm at a couple or few inches above the floorboard. If the pedal continues to sink, it could be a sign of a significant leak in the brake system. This is extremely dangerous and you may suddenly find yourself with no brakes if this is the case. If you have this condition, stop driving the car and contact your mechanic immediately.
A pulsing or grabbing feeling in the pedal when applying the brakes may mean that your rotors or drums need turning because they have warped, or worn unevenly. It may also indicate a problem with your brake calipers or shoes or that their pads and shoes may have worn unevenly. Rotors and drums can warp from over-tightening the lug nuts, overheating, abuse, bad design or a defect. Sometimes, brakes will "grab" if the surface of pads or shoes are contaminated with debris or fluid, such as brake fluid or excess moisture.
If your pedal feels soft, or lacks response, you may have air in your system. Air can get trapped during brake repairs when the the system is not bled or are improperly bled. It is also a sign of damaged components, a leak in the system, or bad braking parts such as a bad caliper on disc brakes or a bad wheel cylinder on drum brakes. Like a sinking pedal, air in the system is potentially dangerous as it could suddenly leave you with no brakes. See your mechanic as soon as possible if your pedal feels unusually soft or unresponsive.
Because any problem in the braking system is potentially dangerous, it is important to pay attention any time your brake pedal feels unusual. Always have your braking system examined (at shops like Care Muffler & Brake Shop) any time you suspect a problem with your braking system. Don't take a chances with your brakes. The problem may be something minor, like an adjustment, or it may mean you need to have major components repaired.