Most of the time, when you step on your brake pedal, the car simply slows down with little to no drama. Then there are other times when you have to brake hard to slow down for a fast-changing light or to get into a crowded turn lane on a highway, and the car shakes when braking.
There are a lot of things that can cause the car to shake when braking. Depending on the road conditions, it might just be the anti lock brake system bringing you to a semi-controlled stop. Though a car that shakes when braking is often an early and/or salient sign of a more serious brake problem, such as worn brake pads, worn rotors, or even a suspension system problem.
To find out why your car shakes when braking, we will have to start with a granular understanding of how the components of your car’s braking and suspension system work together.
How a Braking System Works
A car’s braking system is activated when you step on the brake pedal. This causes the master cylinder to send pressurized brake fluid through the brake lines to the brake calipers on each wheel. The calipers then compress, squeezing the brake pads against a steel rotor disc. This slows the wheel via friction. The ECU then adjusts the engine and transmission as your foot exits the accelerator pedal.
Faults in the brake system can cause the car to shake when braking. Though the most common causes usually come down to bad calipers, worn-out rotors, worn-out pads, suspension, or bearing issues.
5 Surprising Reasons Why Your Car Shakes When You Apply the Brakes
When a car shakes when braking, you can often narrow it down to a problem with the rotors, calipers, or brake pads themselves. However, it’s certainly possible for other faults in the wheels or suspension system to cause or add to the problem.
Troubleshooting the reasons why your car shakes when braking will help you figure out if it’s something you can fix yourself or if you need to pay a mechanic to take care of it for you.
1. You might have Worn-Out Brake Pads
Friction on worn-out brake pads can cause the car to shake when braking. If the shaking happens only when you are slowing down from high speed, such as coming off the highway onto a short on-ramp, it could be a sign that the pads are coming to the end of their life.
If the car shakes when braking at low speeds and you hear a grinding noise, the pads must be replaced immediately. It might be that the car isn’t safe to drive, and/or the worn-down pads could have damaged the rotors as well as the calipers.
Signs of Worn-Out Brake Pads
How to Fix Worn-Out Brake Pads
A brake pad replacement is just within range of what a modestly experienced DIY mechanic can handle. Though usually badly worn pads that cause the car to shake when braking also means there are problems with other components like rotors and brake calipers.
The cost to have a mechanic only replace the brake pads will range from $120 to $250 per axle. Though if the brake pads are badly worn, causing the car to shake when braking, you shouldn’t be surprised if the mechanic strongly recommends replacing the brake rotors as well.
2. Bad Brake Calipers Are also a potential Reason
Badly worn-down brake pads that damage the calipers and rust and damage to the calipers themselves can also cause a car to shake when braking. The calipers respond directly to the hydraulic pressure of the brake fluid in the lines, regardless of the state of the brake pads.
The brake pads may have worn down to the point that parts of the calipers touch the rotors. These surface irregularities can cause shaking that comes and goes. Often times bad calipers will get stuck and depressed, causing an unsettling grinding noise.
Signs of Bad Brake Calipers
How to Fix Bad Brake Calipers
If a bad brake caliper is the reason why your car shakes when braking, you’ll need to replace it as well as the brake pad. You usually need to replace both pads on that axle, and chances are good when you do that; you’ll find that the other caliper is about to go as well.
The actual physical part of replacing brake calipers and brake pads isn’t all that difficult. Though you do need to work with hydraulic lines and bleeding the brakes. If this isn’t done correctly, the car will be unsafe to drive. This is why a lot of people choose to have a mechanic replace their bad brake calipers.
The cost of replacing your brake calipers ranges from $450 to $800 per axle.
3. problem can also occur from Warped or Worn-Out Brake Rotors
Brake rotors that are deformed or worn out from excessive use are one of the more common reasons why a car shakes when braking. Most modern vehicles have four brake disc rotors.
Over time the brake pads and even the tips of the calipers can start to dig grooves in the surface of the rotors. This causes a change in the rotors’ thickness, often described as “Warping” or “Warped Rotors.”
If the warping effect on the brake rotors continues, the car will still shake when braking, even if you completely replace the brake pads with new ones. The difference in the surface texture can be too extreme, and the rotors themselves will need to be replaced.
Signs of Warped Brake Rotors
How to Fix Warped Brake Rotors
Most of the time, when a car shakes when braking due to warped brake rotors, you need to replace the rotors completely. Rotors tend to wear out roughly twice as fast on front brakes as on the back. If you’re lucky, you might only have to replace one set. Though this usually also requires replacing the brake pads as well.
If you’re handy and have the right tools, you might be able to replace your brake rotors and brake pads. This will cost you around $125 to $350 per axle for the parts. Then plan on it taking an entire afternoon to do yourself.
The cost to have a mechanic replace your brake rotors will range from $225 to $500 per axle.
4. Bad Wheel Bearings might be responsible
Loose, worn-out, or bad wheel bearings can lead to an excessive amount of lateral runout, which first shows up as the car shaking when braking. Each of your car’s wheels relies on tightly packed yet freely moving wheel bearings.
The wheel bearings play a critical role in allowing each wheel hub to spin around the mounting point for the wheel and tire. Since the wheel hub is the mounting spot, bad wheel bearings can translate the vibration and shake to the suspension system and the rest of the vehicle.
Signs of Bad Wheel Bearings
How to Fix Bad Wheel Bearings
Replacing your own wheel bearings requires an intermediate level of skill and some special tools that not many DIY mechanics have. If you’re not experienced in this area, then it’s probably best to have a mechanic replace the bad wheel bearings.
The cost of a mechanic replacing one wheel bearing ranges from $225 to $350 per wheel.
5. Suspension Problems from Worn-Out Struts
Worn-out struts and similar suspension system problems can also be a reason why your car shakes when braking. This is because the struts mount brake rotor mounts to the steering knuckle. When you brake hard, the car’s suspension system bears some of the braking force. If the strut itself is worn out, it can vibrate without failing, which makes the car shake.
Signs of Worn-Out Struts
You can usually tell if it’s a strut problem instead of a braking system issue by taking note of the following symptoms.
If you suspect, bad struts are the reason why your car shakes when braking, you will likely also notice fluid leaking out of the struts when you inspect them.
How to Fix Worn-Out Struts
The only want to fix worn-out struts is to have them replaced. Usually, when one strut goes on one side of the car, the other strut on the other side is also bad or about to go. So, it makes sense to have both replaced.
With most vehicles, the front struts wear out twice as fast as the rear, as they bear more weight and endure more stress when braking.
Usually, it’s best to have a mechanic replace your struts, as there might also be problems with the control arm bushings, stabilizer bar end links, and ball joints.
The cost to replace struts usually runs between $150 to $400 per strut, with the cost of the parts being higher on larger, heavier vehicles. At the very least, you’ll have to replace two struts, probably in the front.
Frequently Asked Questions
Is It Possible to Smooth Out Warped Brake Rotors without Replacing Them?
If the deviations in the surface of your brake rotors are minor, a mechanic might be able to resurface them to reduce how much the car shakes when braking. This can save you the cost of replacing the rotors. Though this is the exception more than the rule when it comes to dealing with warped rotors.
Do I Have to Replace the Brake Pads When Replacing Brake Rotors?
If warped rotors were causing your car to shake when braking, it also means that the brake pads are likely deformed as well. If you don’t replace the pads with the rotors, the new rotors won’t make full contact when braking. This can lead to more vibrations, as well as poor stopping distance.
What If My Car Has Brake Drums?
Some older vehicles and trucks have rear brake drums. The material in the drums tends to last a long time, but it can wear down or develop grooves in it, which might be a reason why your car shakes when braking. In a scenario like this, you’ll likely have to replace the brake drum itself.
From Vibrations to Victory
Usually, the reason why a car shakes when braking is due to badly worn-out brake pads, warped rotors, bad calipers, or any combination of the three. These three components all work together, so when one starts to go, it usually starts to affect the others. So, it’s always wise not to procrastinate brake problems for safety and expense reasons.
It might also be possible for bad struts or a bad wheel bearing to be the reason why your car shakes when braking. However, these faults are more common in vehicles that are older or have high mileage.
Fixing any of these components sits right on the edge of what a modestly skilled DIY mechanic can do independently. You often need special tools, and the car will be dangerous to drive if something goes wrong. So, if you aren’t sure that you can handle the repair, it’s wise to have the brake system repaired by a mechanic.
Jason Farrell is a certified master technician, the editor of Mechanic’s Diary in Pittsburgh, Pennsylvania. He is ASE (Automotive Service Excellence) certified and earned a Bachelor’s Degree in Automotive Technology from Pittsburg State University. With nearly 18 prior years of experience in the automotive field, he has extensive knowledge about Domestic, European, and other foreign makes and models of cars and light trucks. Jason’s experience working as a technician and service manager at dealerships, gave him the experience and know-how of most aspects of inspection, diagnosis, and repair from engine and drivability to electrical, HVAC, brakes, steering and suspension and everything in between.