Why Your Car Shakes When You Brake and What to Do About It

As one of the most vital systems on your car, the braking system is responsible for keeping not just you and your occupants, but everyone else around you safe. Over the decades, the braking system has been evolving to efficiently protect persons on the road by providing shorter stopping distance and much needed balance when braking at higher speeds.

Since the braking system is something you use every time you get out on the road, your car’s brakes are prone to different shapes of wear and tear. These issues usually require acting fast in order to maintain optimal braking capabilities of your car.

One of the most common brake-related issues manifests if your car starts shaking during braking. The vibrations could be felt on the steering wheel and sometimes the brake pedal itself, and they usually get more intense at higher speeds or during hard braking. So, what causes your car to vibrate and shake braking? Today, we’ll address this brake system issue and help you prevent it, or diagnose it and solve it on time.

Why is your car shaking when you press the brake.

Before we start, here’s a quick recap of your car’s braking system. Most often, it consists of four discs mounted behind each of your wheels, with four brake calipers hugging them. Many older cars and contemporary subcompacts tend to have rear drum brakes, a system that is not as efficient as discs, but still provides sufficient safety in daily traffic. On the calipers, there are brake pads, an abrasive surface that interacts with the discs when the brake pedal is applied. The whole system is powered hydraulically via a set of brake cylinders that send oil to the brake calipers.

The disc rotors move together with the wheels, and when there’s a need for the car to stop, the press of the brake pedal activates the calipers which grip the disc, thus decreasing the speed of your car.

Modern cars also have a host of electronic systems that make stopping more balanced and quicker, thus safer for everyone involved. Anti-lock brakes disable the possibility of your brakes locking by limiting the grip, effectively shortening stopping distance of your car, while electronic brakeforce distribution ensures that your car travels in a straight line during the braking maneuver.

What Causes Your car to Shake while Braking

Distorted brake rotors are the only cause of your car shaking when you press the brake pedal. The science behind it is simple: the distortion of the brake rotor causes it to alter its axis, and the brake caliper doesn’t get the same amount of grip of the disc. There are several reasons for this issue though, and they all have to do with basic physics. 

One of them is when the disc rotors simply wear out over time, and it usually happens on the front brakes as front discs get worn out faster. As we previously mentioned, the braking components of your car get used every time you take your car out for a drive. As such, the rotors and the brake pads gradually get worn out. The brake pads have a much shorter lifespan than the rotors, and they get changed regularly. However, the discs also get worn during braking and are getting gradually thinner as your mileage progresses.

Braking is a friction-based process, and during it, the rotors and calipers gradually get heated. When a brake rotor has enough material on it, that heat is absorbed and distributed evenly from the outside to the inside. But, as the rotor loses thickness over time, and due to exploitation, it gets harder for it to cool down. That’s why worn out brake rotors sometimes distort under exposure to heat.

The other possible cause of unpleasant shaking while braking are your car’s brake calipers. Like virtually every other part on your car, brake calipers also deteriorate with age and exploitation. Old brake calipers sometimes don’t retract fully when you depress the brake pedal. When the brake caliper fully sticks to the disc rotor, it usually blocks the wheel. This issue is easy to diagnose since it requires immediate reaction. 

However, even if the caliper doesn’t block the wheel, it still creates friction, which of course generates heat. If you don’t notice the smell and decreased performance of your car, you risk your disc rotors overheating, which will again cause them to overheat. Even if your rotors aren’t extensively worn, prolonged exposure to heat caused by friction will overheat them, causing them to distort. If they do, you will again experience shaking and uneven braking.

Overtightened wheel nuts are a rather bizarre, but still a very common reason for brake rotor distortion. Wheel nuts need to be tightened under the same tension. However, if excessive or uneven tension is used, it will cause the brake rotors to warp over time. This process doesn’t involve heat and isn’t anyhow related to your driving style or your maintenance habits, so it’s harder to diagnose it than other causes.

Diagnosing the Issue

If you are suffering from distorted brake rotors, you will experience shaking only when your car is stopping. If there’s shaking on the steering wheel during driving, it’s most likely a tire-related problem or a steering column issue. The shaking caused by warped brake rotors will also be felt on the brake pedal, and more often than not, you will hear a humming sound that will make it easier to determine which wheel is affected. 

Next, knowing your brake change interval is essential for determining the reason for brake disc distortion. These numbers shouldn’t be taken for granted though and depend on your driving style and the roads you drive on. For example, if you live in a mountain area where you often drive up and down the slopes, your brake rotors will wear faster because you’ll be more likely to apply the brakes often while you’re descending. Also, if you had any traffic situations that required hard braking, your brake rotors could overheat from that as well.

Brake rotor distortion due to skipping brake rotor change is more likely to affect the front brake rotors since brakeforce is usually greater in the front due to weight distribution of most cars. 

If you drive a high mileage car and you don’t remember servicing brake calipers, it might be that a caliper didn’t lose its grip on the wheel, causing the rotor to overheat and distort. This could happen to any of the wheels, regardless of the condition of the rotor itself.

Finally, if your car starts shaking not long after you’ve had any service that involved removing the tires, overtightened wheel nuts are the most probable cause of brake rotor warping.

How to Stop the Shaking

In short, fixing this issue requires brake rotor change. However, due to different causes of this problem, the solutions may vary slightly.

In case of overused disc rotor or overtightened nuts, the solution is to replace the brake rotor discs

If the cause of your brake rotor failing are brake calipers, servicing them will also be required in order for your car to function properly again.

What’s important to know is that replacing just one brake rotor is never the right solution. Unevenly worn discs will cause your car to brake improperly, since there’ll be an unequal distribution of brakeforce. So, when you go to the mechanics to get the problem fixed, make sure to replace at least the rotors and pads on one axle, if not on all four wheels.

Ignoring this issue is bad for your car for multiple reasons, and unease while braking is just a tip of the iceberg. Braking with a warped rotor can cause damage and failing of other components like suspension. That will not only multiply your repair costs but also make you potentially dangerous in traffic.

BEST BRAKE GREASE

How to Prevent Distorted Brake Rotors?

The best way to never experience your car shaking during braking is to maintain it regularly and to service your brake system by using high-quality parts.

Performing regular check-ups at your mechanic is vital for your car’s health, so don’t hesitate to ask them to take a look at your discs from time to time. Brake pad replacement isn’t a costly procedure, and that’s always a good occasion to see the condition of your brake rotors and calipers.

If you have thin rims with accessible brake rotors, you can perform a quick brake rotor check up yourself. Before you take your car out on a drive, place your finger on the inward side of your disc, and slowly move it outward. If you feel a big difference in thickness or even the slightest cracks, your disc rotors are due for inspection, if not replacement. Be sure not to perform this test after long or intense drives because you might only end up with a burned finger.

Also, if you have a high mileage car, servicing your brake calipers during each brake rotor replacement is a good way to avoid potential brake caliper malfunctions. That will bring your maintenance costs up, but it could prevent your brand new disc rotors to warp suddenly.

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