Sometimes depressing the brake pedal while the car is in motion can cause the vehicle to shake and vibrate, which can be unnerving. You’ll feel most of this vibration in the steering wheel and the brake pedal. Not to worry, as this is a fairly common issue.
Potential reasons as to why this might be happening:
Brake rotors or drums:
Depending on your vehicle, and whether you’re looking at the front or rear brakes, you’ll have either brake rotors or brake drums. The rotors and drums are attached to the wheel, and when you depress the brake pedal, the brake pads put pressure on the rotors and drums, which slows down the wheel. Over time the rotors and drums can become warped, especially if they’ve been exposed to lots of heat. This creates a wobbly effect when the pads come into contact with the rotors or drums: the pads will only come into contact with part of the rotor, which makes for a sporadic and pulsating effect.
Your car relies on flush contact between the rotors or drums and the pads for a smooth braking experience. Just as warped rotors and drums prevent this, warped pads do, too. If a brake pad is warped, it will make inconsistent contact with the brakes when you apply the pedal, and the braking will not be constant. Brake pads can also accumulate dirt, debris, and rust, which can result in shaky braking.
Wheel bearings and lug nuts:
Wheel bearings and lug nuts serve to make your car’s wheels a tight and smooth running operation. They help the wheel, tire, and hub work in unison for consistently smooth driving. When the bearings or lug nuts are loose, the wheels become wobbly. You may not notice this while you’re driving, as the momentum will help the wheels move smoothly, but as soon as you break, the wheels will begin to wobble and the whole car will shake.
Having your wheels aligned is an important part of vehicle maintenance. When a car leaves the factory, it is perfectly aligned: each wheel is at the exact right angle so that all four wheels share the work of the road, and help the car drive straight. Over time – especially if you’ve had damage to the suspension of your car – your wheels will fall out of alignment. The tires may angle in or out, and they may be uneven. Just like with bearings and lug nuts, you may not notice this lack of alignment when you’re accelerating or moving at a constant speed, but it will result in uneven braking and premature tire wear.