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Why Does Your Car Shake When You Brake

Picture of the brake rotors for car shakes

Learn Why Does Your Car Shake When You Brake Or Accelerate

Driving a car that shakes or shudders during braking can be unsettling. Not only are there worries about repairs and costs, but concerns arise about vehicle safety. It’s an issue that needs attention right away. Read on as we explore answers to the question, “Why does your car shake when you brake?”

Malfunctioning Brake Rotors

Braking works by the calipers moving the brake pads against the brake rotors . The resulting action causes friction which slows and then stops a car. The surface of the rotors must be smooth to ensure proper brake pad contact. So, wear and tear issues can be one answer for the “Why does your car shake?” question.

Warping: The walls of the rotors can thin out due to everyday use. As a result, the rotors bend and warp as a byproduct of the heat that occurs during braking. A misshapen rotor prevents the pads from evenly applying friction to the discs, and vibration occurs. Pay attention to a steering wheel that shakes when braking as a red flag for this issue.

Uneven Wear: It’s not unusual to come across uneven rotor wear with results similar to what you’ll find with warping. This is also the case if the rotors were replaced with cheap alternate components.

Abrasions: Worn-out or poor-quality brake pads can score or scratch the rotors (look for indentations or tracks along the rotor surface as a clue). A screeching sound along with vibrations is another tell-tale sign that the rotors have seen better days.

Worn Brake Pads

Brake pads that are past their prime are another cause of car shaking or shuddering. You’ll feel a vibration as the pads’ wear indicator sounds off with a squeal. This warning device is a metal tab that signals (through metal-on-metal contact) it’s time to replace the brake pads.

Worn brake pads can damage the rotors and make for a much more expensive repair job. So, ignoring the warning signs can create a safety hazard and empty more of the wallet. And, like brake rotors, pads can become damaged or warped, which causes vibrations like with bad rotors.

Other Brake Issues

Seized Brake Calipers

A stuck brake caliper can lead to inconsistent pressure on the brake rotors. This uneven pressure can lead to vibrations.

Stuck Guide Pins

Essential components of brake calipers are guide pins. These small but vital parts properly align the brake pad against the rotor. A stuck pin, usually caused by insufficient lubrication, impedes the regular operation of the brake pad. Or causes the caliper to stick. Either situation causes a car to shake during braking.

Air Contamination in the Brake Lines

Soft or spongy-feeling brakes are a classic indicator that air has entered the normally closed braking system. As a result, uneven pressure gets sent to the calipers, making the pads push unevenly against the rotors. It adds up to another opportunity for car shaking during braking.

Distorted Brakes Drums

Excessive heat during braking can cause a brake drum to reshape and become out-of-round. Vibrating can happen as the linings get pressed against misshapen drums during the braking process.

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Tire and Wheel Troubles

Unbalanced Tires and Wheels

Tire and wheel balancing ensures the weight of the set is evenly distributed for smooth driving, safe stopping, and better fuel economy. The loss of a balancing weight or striking a pothole can put things out of whack, which can become noticeable during braking.

Worn-Out Tires

Tires can get worn out from everyday use or a misaligned suspension, to name a few reasons. Uneven tire treads can then lead to car vibrations which may be noticeable during braking, acceleration, or deacceleration. It’s the car’s way of telling you that something needs attention.

Damaged Wheels

Like tires that are no longer in ideal condition, a bent wheel can cause an imbalance. This condition can present itself as vibration.

Loose Lug Nut

Although not a common occurrence an untightened lug nut can cause the wheel to wobble. And a wobbly rim can vibrate, especially at slower speeds.

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Alignment and Suspension Problems

Alignment Issues

Vibrations during braking can also be a symptom of a car with a bad alignment. At the same time, misalignment can cause premature tire wear and affect the suspension.

Failing Steering or Suspension

When all else fails, see if the steering or suspension is the culprit for vibrations or shuddering during braking. Bad ball joints and tie rods can show up as vibrations during braking or turning.

Also, a defective CV joint can cause car shakes at high speeds or while braking. Remember that the symptoms can be similar to what you’d feel from an unbalanced wheel, so be sure to thoroughly investigate the cause.

Why Does Your Car Shake When You Accelerate?

Now that we’ve covered what causes a car to vibrate during braking, let’s look at what causes the same effect during acceleration. As we covered earlier, some problems may appear during braking, accelerating, or both. Keep in mind, car troubles may not present themselves according to textbook guidelines.

Broken Engine Mounts

Engine mounts ensure that a power plant is secured correctly to the vehicle’s frame. In addition, engine mounts help lessen the engine vibration that would otherwise get transmitted throughout the car and make for an unpleasant ride.

Engine mounts are usually made of rubberized composite to best absorb vibrations. Some high-end components may even be liquid filed. But, exposure to extreme temperatures (from both the engine and the outdoors) and engine motion can eventually take a toll on an engine mount.

Vibration during acceleration is one of several broken engine mount warning signs. You may also notice the car shaking when idle (or car shaking when stopped). Remember that one damaged mount will put a strain on the other mounts. Not only can more engine mounts break, but this can lead to misalignment of the engine and damage to other components.

While you may not have to replace all engine mounts, it’s not a bad idea to do so to prevent a repeat of the situation.

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Damaged Driveshaft

A driveshaft transmits power from the engine to the rear axle in rear-wheel-drive or all-wheel-drive/four-wheel-drive vehicles. This component requires careful balancing to correctly send power to the connected wheels.

Road debris or an accident can damage the driveshaft and result in vibrations while driving. This may be observed somewhat during low speeds. But you may notice the car shakes when driving over 70 mph.

In most cases, a driveshaft requires replacement, not repair. And some driveshaft materials (aluminum and carbon fiber) are more susceptible to damage than the traditional steel driveshaft.

Damaged Axle

No car component is impervious to damage. And while an axle is engineered for long-lasting endurance, it’s vulnerable to ruin when driving over a curb, striking a rock, or during an accident. A symptom of a bent axle is shaking, which gets worse as the car accelerates.

Unfortunately, replacing an axle (usually not fixable) is a significant repair. But there’s no escaping the work if it’s needed.

Malfunctioning Vacuum Hose

Sometimes the simplest thing can cause a car to vibrate or shake. We’re talking about a leaking or disconnected vacuum hose. In this situation, insufficient air pressure can wreak havoc on a car’s sensors and computers. The resulting backfires, power loss, and misfires may seem like the end of the world. But, replacing or reattaching an affected hose can solve the problem without too much fuss.

Consider swapping out a damaged hose with a more robust silicone hose replacement. And don’t hesitate to use a clamp if you find a stretched-out hose-end (it will just become loose again otherwise).

Fouled Spark Plugs

When was the last time you replaced the spark plugs? If you’ve got an older car that’s shaking, consider this a possibility for the problem. Dirty spark plugs can lead to engine misfires. Trouble happens by using cheap gas or simply ignoring recommended maintenance guidelines. Remove a spark plug or two to check for a burnt-looking buildup on the tip.

Other Problems

Clogged Fuel Injectors

Disruptions to the fuel supply can cause car shakes at idle that smooth out while driving. This can involve the fuel injectors or fuel intake system getting clogged with dirt over time. Where does the dirt come from? This is primarily from impurities in the gasoline or debris from the gas tank (a reason to never let the gas gauge go to empty).

Blockages interfere with the normal flow of gas and the combustion cycle. Leading to a shaking engine and car.

Worn Timing Belt

Not every car uses a timing belt (some use timing chains), but those relying on a rubberized belt to connect the camshaft and crankshaft (and other components) can begin to shake as the belt fails. The timing belt is an internal structure, but the same thing can happen to the more noticeable serpentine belt, which powers things like the power steering pump and air conditioning compressor.

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