Ah, the dreadful groaning sound when braking at low speed due to a stick slip between brake pad and disc. It’s an issue that many vehicle owners are all too familiar with, and one that can be infuriating at times. Fortunately, while it can be quite the conundrum trying to uncover the exact issue, there are some simple troubleshooting steps available to try and pinpoint the source of the noise and make any necessary repairs.
There can be several reasons for creaking, or groaning noise when braking at low speeds. The most common cause of a creaking or groaning noise when braking at low speed is the sticky caliper pins as they might need lubrication. Other reasons include worn-out brake pads, spongy brake pedal, damaged wheel hub bearing and warped brake rotor/disc. The brake pad material binds up a little with the brake rotor on a flat surface at low speeds. You should check if the brake pads are unevenly worn out. If the groaning noise when braking is coming from the rear of the vehicle, you should check the drum brakes as they are usually installed on the rear wheels. Sometimes, the lug nuts of the wheels are not tightened to the given specs, due to which brake drums become loose and do not make proper contact with the rear brake shoes. Also, if the wheel is misaligned, it will make the brake disc slightly off-true. This will cause the pads to connect and disconnect repeatedly when braking slowly.
Note: If you have recently replaced brake pads and discs, it is important to perform a brake bedding procedure to break in the pads.
Bonus Read: You can also read my guide on groaning noise when reversing.
Table of Contents
Causes Of Groaning Noise When Braking At Low Speed
Here are the causes of the groaning noise when braking at low speed:
1. Sticking Caliper Pins
Caliper pins are cylindrical guide pins that are usually positioned in the back of the caliper, and connect the caliper to the brake pad with the brake piston. Their purpose is to guide the proper angle for how the brake pad meets the disc. As the brakes are applied, the caliper guide pins help control the angle of the brake pad, ensuring that the pad is pressed firmly against the disc.
When a brake pedal is pressed, the brake oil pushes the piston to press the brake pads against the rotor. As a result, the force acts on the caliper in the opposite direction. The caliper moves along the caliper pin, due to which the brake pad on the other side presses against the brake disc.
In order to understand the purpose of a caliper pin, I have attached a short clip of a Youtube video below:
If the caliper guide pins become stuck and won’t move properly, the brake pad can’t make contact with the disc correctly, resulting in a groaning noise when braking at low speed. This is because the brake pad is not being pressed firmly against the disc, and the uneven contact is causing the noise.
How to spot?
If you have a sticking brake caliper, it will be hotter than calipers on other wheels.
Stuck caliper guide pins can be a real pain to deal with! Most of the time, corrosion is the culprit behind it, as steel pins that are exposed to salt and water can quickly form rust. But don’t forget about dirt and debris that can accumulate around the caliper guide pins and make them stick. And of course, improper lubrication can also cause the pins to become stuck.
Furthermore, behind the caliper guide pins is a rubber boot. The rubber boot encloses grease to keep caliper pins lubricated.
How to fix?
Clean the brake caliper pins with a wire brush to remove dust, debris, and signs of rust. Once the caliper pins have been cleaned, apply a thin layer of lubricant to them. This will help ensure that the pins move freely and prevent them from sticking.
Note: Always use recommended silicone paste to lubricate the caliper pins. Furthermore, if too much lubricant is applied to the slide pins, air can be trapped at the end of the pin creating an “air spring”. This condition causes the caliper/pad assembly to drag on the rotor.
2. Wheel Is Not Tightened Properly
If you’ve recently got installed brake pads, the chances are that the lug nuts of the wheels are not tightened properly, due to which your vehicle makes groaning noise when braking at low speeds.
When the wheel is not tightened properly, it can lead to a whole host of problems. When you apply the brakes, the wheel can wobble (move side to side) slightly, creating an unpleasant groaning noise. Not only is this noise irritating, but it can also cause excessive wear on the brake pads, resulting in costly repairs.
How to spot?
If you hear a strange groaning sound when you press the brake at low speeds, the first thing you should check is the wheel nut – make sure it is torqued correctly with a torque wrench. If it’s not, you need to tighten it to the manufacturer’s specified torque rating.
Furthermore, make sure that the lug nuts of the wheels are tightened in a correct star pattern. Failure to do so will cause the wheel to go out of balance which will eventually result in the warping of the brake disc and groaning noise.
Also Read: Steering wheel turns automatically
3. Damaged Wheel Bearing
Wheel bearings are an essential part of any vehicle and are located at the wheel hub. Wheel bearings provide the necessary support for the wheel and axle, allowing the wheel to move freely. Unfortunately, over time wheel bearings can become worn and damaged, leading to a whole host of problems. One of which is an annoying groaning noise when you apply brakes at low speed.
Corrosion can cause the surface of the wheel bearing to become pitted, which can reduce its efficiency and cause it to wear out more quickly. Furthermore, if a vehicle is overloaded, this can put additional strain on the wheel bearing, causing it to wear out more quickly.
How to spot?
To spot bad a wheel bearing, jack up the vehicle. Hold the wheel at the top and bottom, and shake vigorously. Then hold at the left and right and shake. If there’s some play then either your wheel nuts are loose or you’ve got play in your bearings.
4. Brake Rotor and Pads Are Not Bedded
When you install new brake rotors and pads (make sure they are OEM), it is normal that for some days they will produce groaning noises when braking at slow speeds. This is because pad material binds up a little with the brake rotor when it is new. New brake rotors are glazed and do not grab well with the brake pads, due to which your vehicle produces groaning noise when braking at low speeds.
Bedding is a process by which the brake rotors and pads are worn in to create a more uniform friction surface, which helps them to work together more efficiently. In this way, brake pads and rotors can work together to provide a smooth, quiet brake experience.
When the brake rotors and pads are not bedded, the friction surface may not be uniform, which can cause uneven braking performance. This can lead to excessive brake noise, vibration, and, in extreme cases, brake failure.
How to do?
To bed your brake rotors and pads, you’ll need to engage the brakes several times in a row. Bedding in brakes should be done on a flat, straight stretch of road. Doing so on a curved or hilly road could cause the vehicle to skid or slide.
To bed the brakes, you will need to lightly press on the brakes at a low speed and then come to a complete stop. This process should be repeated several times, increasing speed each time. After a few cycles, you will begin to feel the brakes become smoother and quieter.
So, drive the vehicle at a speed of 60mph and slow it down to 5mph speed with fairly heavy braking without coming to stop. This will raise the temperature of brake components sufficient for the bedding of brakes. Make sure that you do not press the brakes too hard as it will activate ABS. Repeat this process 10 times.
5. Warped Brake Disc
When you hear a loud groaning sound while braking your car at low speed, it could be a sign that your brake discs are warped. Warped brake discs are a serious issue as they can lead to compromised braking performance, reduced efficiency, and even serious safety risks. When the brake disc is moving slowly at low speeds, it can’t overcome the resistive forces caused by uneven wear on the brake disc.
The most common cause of brake disc warping is scoring on the rotor. This occurs when brake pads become too worn or contaminated with dirt, debris, and other particles. These particles come into contact with the rotor, creating a grooved pattern and causing the rotor to become bent or warped.
Another factor that can lead to brake disc warping is corrosion. Corrosion can occur when the brake disc is exposed to salt, water, or other corrosive materials. If left unchecked, corrosion can cause the rotor to become warped and result in a groaning noise when the brakes are applied.
Glazing of the brake pads can also lead to brake disc warping. Brake pads are made of a soft material that is designed to wear down over time. However, if the brake pads become too hot, they can harden and form a glazed surface. This glazed surface will cause the brake disc to become warped, resulting in a groaning noise when the brakes are applied.
How to fix?
If brake discs are just corroded, use a wire brush to remove dirt and corrosion. Then use CRC brake cleaner to clean the brake discs. You can also use Isopropyl Alcohol to clean brake discs.
6. Spongy Brake Pedal Or Bad Brake Fluid
A spongy brake pedal can lead to a disconcerting groan when braking at lower speeds. This is often caused by inadequate pressure in the brake lines, which prevents the brakes from working properly. This can present itself in a more subdued brake pedal than usual and a groaning sound when applying the brakes.
If the brake fluid is contaminated or its level is low, the pressure in the brake lines can drop and air can be drawn into the system. This creates a spongy sensation in the brake pedal.
The step in diagnosing this issue is to check the level of brake fluid in the master cylinder and the brake fluid reservoir. If the brake fluid level is low, then you need to top it up with the correct brake fluid and bleed the brakes. This will remove any air in the system and restore the pressure, allowing the brakes to work normally again.
In the below Youtube video, you can learn how to bleed your brakes by yourself:
7. Worn-out Brake Pads
When you hear a groaning noise while braking at low speed, it may be a sign that the brake pads are worn out and need to be replaced. Brake pads are an essential part of your vehicle’s braking system and their wear and tear is inevitable over time.
Bonus Read: Grinding noise when braking but pads are fine
Brake pads are composed of three distinct components: a metal backing plate, a pad of friction material, and a wear indicator. The metal backing plate acts as a stabilizer, securing the pad to the brake caliper, while the pad of friction material generates the friction required to decelerate or stop a vehicle.
The brake pad’s friction material can become thin and worn-out over time, reducing the amount of friction between the pad and the brake rotor. This, in turn, weakens the brake system capacity to slow down or stop the vehicle, which can result in a groaning sound when braking at low speed.
When it comes to braking at low speed, one of the most common sources of groans is aftermarket brake pads. These brake pads are typically different in size than the factory-installed varieties, resulting in uneven wear and ultimately, an audible noise when slowing the vehicle.
The size of the brake pads has an immense effect on your vehicle’s stopping power. If the brake pads are too small, the contact between the pads and rotor is restricted, thus causing an ineffective braking performance. But, if they are too large, they may be in contact too much with the rotor, which may cause excessive wear and tear.
Furthermore, if the wrong size brake pads are selected, it can cause issues such as the pads not being aligned with the rotor, chamferring wearing off quickly, and the pad chucking back and forth in the caliper.
When selecting the brake pad size, it’s important to consult the vehicle manufacturer’s specifications. This will help you determine the exact size of the brake pads that are recommended for the vehicle.
How to spot?
To spot a bad brake pad, use a gloved finger to feel the surface and see if you can feel anything like a bumpy or overly gritty texture. If so, you can use some very high-grit sandpaper (200 or 300 grit) to scuff the bumps or overly gritty texture and see if you can dislodge anything embedded into the pad surface.
8. Damaged Upper and Lower Control Arm Bushings
Control arms are a vital part of your vehicle’s suspension system as they connect . Upper and lower control arm bushings are rubber bushings located between the control arms and the vehicle’s frame. They act as a cushion between the two parts, absorbing the vibration and providing smooth movement between the control arm and the chassis.
Contorl arm bushings are responsible for keeping the suspension components in place, and if they are worn or damaged, they can cause the suspension to move around more than it should. This movement can create a groaning noise as the components rub against each other. In some cases, the groaning noise can also be heard during normal driving, as well as when turning at low speeds.
How to spot?
Control arms connect steering wheel to the vehicle’s chassis via steering knuckle. If the control arm bushings are damaged, the steering may become loose and difficult to control due to the suspension being out of alignment.