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A shaking or pulsating when applying the brake pedal almost always indicates excessive rotor runout or a variation in rotor thickness. Although not quite accurate, many professionals refer to these irregularities as “warped brake rotors.”

Of course, there are also some other, less common reasons why your car might be shaking when braking.

foot pressing brake pedal
Excessive rotor runout or variation in rotor thickness can cause your car to shake when braking.

Why Does My Car Shake When I Brake?

Worn rotors are the most common cause of shaking while braking. But there are other potential reasons for the sensation, as well. Here’s a quick rundown on five possible causes:

Excessive lateral rotor runout or a variation in rotor thickness (warped brake rotors)

Many modern cars have disc brakes at all four corners, though some have discs in the front and drums in the rear. Pressing the brake pedal forces a pair of brake pads to squeeze against the disc-shaped rotor, creating the friction needed to stop the vehicle.

Over time, the brake rotors can develop irregularities, such as excessive runout or a variation in thickness (also known as parallelism). Runout refers to a distortion of the rotor that causes it to wobble side-to-side as it rotates. Thickness variation, on the other hand, indicates the rotor is thicker in some spots than others.

Both concerns can prevent the pads from pressing squarely against the rotor during brake application. The result is often a shaking/pulsation sensation felt in the brake pedal. Because the brakes mount to the wheel hub, which mounts to the steering knuckle, you may also feel shaking in the steering wheel.

Out of round brake drums (if your vehicle has drum brakes)

Some vehicles still have drum brakes in the rear. With this design, when the driver presses the brake padel, a pair of brake shoes are forced outward against a brake drum, creating friction.

Brake drums that are worn out of round can cause a shaking/pulsation sensation when the brakes are applied.

drum brake of a car
Brake drums that are worn out of round can cause a shaking sensation when brakes are applied.

Loose wheel bearings

There is a wheel bearing behind each of your car’s wheels. Each wheel bearing allows a wheel hub, which acts as a mounting point for the wheel and tire, to turn as the vehicle is traveling down the road.

Because the wheel hub also serves as a mounting spot for the disc brake, a loose wheel bearing can lead to excessive lateral runout. As a result, you may experience a shaking sensation while braking.

Worn suspension components

In some cases, worn suspension components can cause a shaking while braking. The sensation may be felt in the steering wheel and/or brake pedal.

For example, in a strut-style suspension, the brake rotor mounts to the steering knuckle, which, in turn, mounts to the strut. As such, problems with the strut assembly can cause a shaking while braking.

worn brake pads
Worn brake pads also have the potential to cause shaking when the driver applies the brakes.

Worn brake pads

Pulsation and shaking can occur whenever the pads don’t apply squarely against the brake rotor. That means worn pads also have the potential to cause shaking when the driver applies the brakes.

What to Do About Brake Pedal Pulsation or Shaking

A pulsating or shaking brake pedal can affect braking performance, thereby compromising vehicle safety. You should address the issue as soon as possible.

If you have the know-how, fixing the problem yourself is usually fairly straightforward. But if you have any doubts about your abilities, it’s best to let a professional repair the issue. After all, we’re talking about your brakes here.

And your car’s brakes aren’t something you want to gamble with.

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Kani D Gray

I have a 2007 Lincoln MKZ it’s shakes breaking I did everything from new tires to rotors to breaks to calipers to tie rod ends and it’s still shaking when I break over 45mph help please

CarParts.com

Hi Kani,

Unfortunately, there isn’t a one-size-fits-all answer to your problem. The issue could be anything from loose wheel bearings to worn-out suspension parts. It’s also possible that the rotors weren’t machined properly if you had them resurfaced rather than replaced.

To get to the bottom of the problem, I recommend getting an in-person diagnosis from a reputable repair shop.

-Mia, Chief Mechanic @ CarParts.com

Fredrick Rehders

Ms. Mia, wrote a very insightful piece, here. I question the reason she chose the ’87 Cavalier, though. Unless of course, she just loves a challenge. The ’80s produced the absolute worst generation of American made cars, in my humble opinion. I own an ’84 GMC Dually, that has been an excellent truck, especially after replacing the engine and tranny.

CarParts.com

Hi Fredrick,

I was born in the 80s, so I’m drawn to the cars of that decade. Also, I think vehicles got a lot better in the late 80s when fuel injection and computer controls started to become commonplace. I recently wrote an article on the subject: https://www.carparts.com/blog/why-you-should-buy-an-80s-car/

I have two Z24s, (an ’87 and an ’88) and the ’88’s odometer stopped working at 240k miles. According to the previous owner, the engine and trans are all original, though the engine had some top end work done at one time.

That being said, the cars from the 80s are over 30 years old now, and age takes its toll on everything. That’s why my daily drivers are an ’07 Honda Civic and an ’01 Toyota Tacoma 4×4.

-Mia, Chief Mechanic @ CarParts.com

Fredrick Rehders

I really did not expect a reply, but thank you! I have the restored ’67 El Camino, that was my daily, when I met my wife, 31 years ago.

We acquired her dream car a few years ago. It is a ’69 GTO Judge Ram Air IV. Our other works-in- progress are a ’68 Corvair Convertible and a ’64 Corvair Spyder turbo coup.

I assure you, we do understand era specific nostalgia. I just do not work on computer controlled vehicles. I am just a dinosaur, that had a lot of trouble working on every car I owned in the 80s.

I was out of my lane and tip my Resistol to you. You have tamed what I failed to try. Best regards!

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