3 Common Reasons Your Car Shakes When Applying The Brakes
Few things are more unnerving than feeling your car shake or shutter when you apply the brakes, especially when it happens at high speeds. Let’s face it, the shuttering and steering wheel shake from brake pulsation can be alarming, especially if you’re not sure what’s causing it. In this article, we’ll explore why your car shakes when applying the brakes, and what you can do to fix the problem.
Car Shakes When Applying The Brakes? What’s Wrong?
Noticeable brake pulsation is an annoying and scary experience. If your car shakes when applying the brakes it’s important to find out the cause, your safety may depend on it. That’s why in this article I will cover a few of the common causes of brake pulsation and what may be the root cause.
Let’s get started…
What Is a Brake Pulsation?
Brake pulsation is a situation where one or a combination of one issue causes your vehicle to shake or shutter when hitting the brakes, especially at higher speeds.
Symptoms of a brake pulsation:
There’s a few possible reasons why your car shakes when you apply the brakes. Your vehicle may have one or a combination of the issues listed below, let’s take a look.
Warped brake rotors:
Warped brake rotors is the most common reason your car shakes when applying the brakes by far. Brake rotors are the thick metal discs that the brake pads contact under high pressure.
The picture above shows a typical disc brake setup, the caliper, pads, and rotor. Notice how the rotor looks worn and “streaked.”
What is the brake rotor’s job?
The job of a brake rotor is to turn the rolling energy of your car into heat, this is how you slow down. Remember in physics class?… Energy can’t be created or destroyed? Same principle here, the brake rotor needs to absorb large amounts of rolling energy over and over again, getting super hot and cooling off again thousands of times in the process.
This is why high performance cars have HUGE brake setups, really fast cars need to slow down really fast without fail.
The constant beating of heating up and cooling down while absorbing large amounts of energy over and over again can cause brake rotors to become warped When the rotors are warped, the brake pads clamp down on a spinning, uneven surface. If your car shakes when you brake, especially at higher speeds, chances are you have warped brake rotors.
What about brake drums?
Brake drums use the same principal as rotors, just in a different design. A brake drum setup uses brake shoes and a wheel cylinder that forces the brake shoes into the drum, most newer vehicles use the disc brake setup these days however. The brake drum resembles a top hat. Brake drums can warp as well, causing the same feelings warped rotors do.
If you suspect that your brake rotors or drums are warped, it’s important to have them inspected and replaced if necessary. Whether you’re gonna tackle the job in the driveway or trying to explain to your mechanic what is going on with your car, this article has you covered.
How to narrow down a brake pulsation
Front or rear? How to tell whether the warped rotor or drum is in the front or rear of your car…
Each wheel has a rotor or drum that can be the reason your car shakes when applying the brakes. How do we know what to replace? Nobody wants to spend money and time on things their car doesn’t need, how can you tell where the cause is? Front or rear?
Here’s a quick tip to narrow down whether the shaking while braking is from the front or rear of your car.
- Drive the car up to speed and apply the brakes.
- Once you begin to feel the vibration pay attention to the steering wheel.
- Repeat this a few times.
What are you looking for?
If the steering wheel wobbles side to side quickly the issue is in the front brakes. The rear brakes are not connected to the steering rack or front end components, therefore if the steering wheel shakes in your hands it MUST be the front rotors causing it. There is a chance your brake pulsation is at the front and rear of the car, however the fronts are definitely involved if it’s felt in the steering wheel.
If the issue is in the rear your car will shake when you brake, but the steering wheel won’t be affected. This quick brake pulsation test is usually spot on for narrowing down the right axle causing the issue.
What causes brake rotors to warp and pulsate?
The usual suspect is heat, drivers that “ride the brake” and stop abruptly have the most issues. Other causes can be a bad brake caliper causing “brake drag” and overheating.
Believe it or not, improperly installing wheels by over tightening and torquing unevenly can also warp a brake rotor. Always be sure to torque your lugs by hand in a star pattern to the correct specification.
Worn suspension components:
It’s possible your car shakes when you brake due to worn suspension components. The suspension system in your car is what keeps the “rubber on the road” so -to-speak and there’s many components that make up a vehicle’s suspension.
Worn out suspension components can cause brake pulsation, it’s a combination of a slightly warped rotor, and a worn out or torn bushing.
In the case of a worn suspension component however, the pulsation can be greatly amplified.
Let’s take a quick example…
A worn thrust arm bushing
Many cars, especially German cars have what is what’s called a “thrust arm.” A thrust arm is located at the front of the vehicle. This arm connects to the front portion of the subframe. From there the arm travels to the spindle (which is where the wheel is attached) and connects with a ball joint.
The front rubber bushing is designed to hold the suspension in place and absorb bumps. Depending on the length and design of this arm, “caster” is achieved. I won’t dive too far here, just know for the sake of this article the rubber bushing is important.
When the thrust arm bushings tear or wear out they lose the ability to dampen and absorb the pulsation, making a slightly warped rotor amplified 10 fold. Common suspension components that can cause this problem include worn or damaged shock absorbers, bushings, and ball joints.
Other things that can cause your car to shake while driving
In addition to the common causes above, there are other factors that can contribute to your car shaking while driving. For example, if your wheels are out of balance, it can cause the car to shake, especially at higher speeds. Out of balance driveshafts and bad CV joints can also make for a rough ride.
If your car shakes when you are not moving this may be due to a misfire or other issue in the engine. This is a subject for a different article but I wanted to put it out there.
How to fix the problem
So, what can you do to fix the problem? The first step is to read this article to understand what makes cars shake under braking, take the time to perform the “quick test ” listed above. If you are a do-it-yourself mechanic you can find a replace the component causing the pulsation.
If you are not that comfortable working on cars have your car inspected by a qualified mechanic. They will be able to diagnose the problem and recommend the best course of action.
In most cases, this will involve replacing worn or damaged brake pads or rotors, repairing or replacing damaged suspension components. Also if your wheels are out of balance or your tires are worn or damaged, you may need to have them balanced or replaced as well. There are at times “oddball” situations that will take an experienced mechanic to sort out.
In conclusion, if your car shakes or vibrates when you apply the brakes, it’s important to get it fixed ASAP have it inspected by a qualified mechanic as soon as possible or get out the wrenches on a Saturday. Cars shaking when applying the brakes can be caused by a number of different factors, including worn brake pads or rotors, warped rotors, loose or damaged suspension components, and possibly more. Identifying and getting these issues fixed can save you time and aggravation down the road, not to mention keeping you and your loved ones safe on the road.
Scoot is a Dad, ASE certified mechanic, and blogger. He has been in the automotive business for over 25 Years.