Types of Brake Pad Wear and Damage
Brake pads are an essential component of any vehicle’s braking system. They are responsible for creating friction to slow and stop the wheels when the brake pedal is pressed. Properly functioning brake pads are critical for safe driving. As the brake pads wear down from normal use, they will eventually need to be replaced to maintain maximum braking performance.
There are a few common types of brake pad wear and damage that can occur over time. Being aware of the signs of brake pad issues allows drivers to address any problems promptly through maintenance, repairs or replacing worn pads. This helps ensure the braking system continues operating safely and reliably.
Normal Wear
Normal wear of brake pads occurs through the natural and expected friction that happens during braking. As the brake pads repeatedly make contact with the brake rotor when braking, the friction material on the pad gradually wears down and reduces in thickness over time and use (source). This is a normal and expected type of wear. Signs of normal wear include the brake pads wearing down evenly between the inner and outer pad, as well as having a smooth wear surface on the friction material. This even and gradual wear pattern indicates the brake pads are wearing normally through regular use.
Uneven Wear
Uneven wear is when one brake pad wears faster than the other. This can happen due to a few common issues with the brake calipers:
If the caliper slides become stuck or seized, it can prevent one brake pad from retracting properly. This will cause the pads to wear unevenly, with one pad dragging and wearing down faster. Proper lubrication and maintenance of the caliper slides is important to prevent this issue (https://www.jiffylube.com/resource-center/identify-and-fix-uneven-brake-pad-wear).
A brake caliper piston that is sticking can also cause uneven pad wear. The piston may not be retracting fully, which keeps pressure on one brake pad even when braking is not occurring. This constant contact with the rotor wears the pad down faster.
Finally, a warped or damaged caliper bracket can allow the caliper to tilt or twist. This misalignment puts more force on one pad than the other, leading to uneven wear. The bracket may need to be replaced to properly realign the caliper.
Uneven wear will make braking performance poor or unpredictable. It’s important to address caliper issues right away before accelerated uneven wear ruins the pads and rotors.
Glazing
Glazing occurs when the friction surface of the brake pad becomes smooth, hard, and shiny due to excessive heat buildup during braking. This is often caused by heavy or repeated braking, such as driving in stop-and-go traffic or descending long hills.
The high temperatures can alter the chemical composition of the pad material, causing it to harden and become glass-like. This glazed layer prevents the pad from gripping the brake rotor properly.1 As a result, braking performance and friction are reduced, leading to longer stopping distances.
Glazing significantly decreases the effectiveness of the brakes. Visually, glazed brake pads will appear shiny or glossy compared to new pads. The surface will become very smooth, with minimal texture. This is a clear sign that the pads are hardened and unable to grip the rotors well. Vehicles with glazed pads will often exhibit poor braking ability, increased stopping distances, brake squeal, vibrations, and other issues.
Cracking
One type of brake pad wear and damage is cracking, which involves visible cracks or fractures in the pad material. This can occur due to a few reasons:
As brake pads age, especially if they are subjected to temperature extremes, the binding agents in the pad material can start to break down and dry out, leading to cracking (1). Prolonged exposure to moisture can also degrade some brake pads over time. Additionally, during the manufacturing process, if brake pads are not properly cured, it can result in material cracking down the road.
Cracks are problematic because they reduce the integrity and strength of the brake pad. Cracked pads are prone to further chipping and breaking under braking pressure. The cracks and fractures also interrupt the friction surface, leading to uneven braking power. Significant cracking is a sign that the brake pads are no longer safe and need immediate replacement.
Drivers may notice a cracking noise when applying the brakes as the pad disintegrates. Visually inspecting pads during tire rotations or brake service can identify any obvious fractures. Replacing cracked brake pads reduces the risk of brake failure and restores smooth, even braking power.
Chipping/Breaking
One issue that can occur with brake pads is chipping or breaking of the pad material. This is where small pieces of the pad material become separated or break off completely. According to this Reddit thread, chipped and broken pads can be caused by the pads being too hard, resulting in the pad material chipping away at the braking surface.
Chipped and broken pads are often a sign of improper installation or foreign objects getting lodged between the pads and rotors. As explained in this article, brake dust and debris buildup can get stuck between the pads and rotors. When you apply the brakes, these particles act like sandpaper, grinding away at the pad material and causing chips and breaks.
Replacing chipped and broken pads is important not only for performance, but also safety. Damaged pads will not grip the rotors as effectively, reducing braking power. Severely chipped pads can also let loose debris into the brake system, potentially causing further damage or brake failure.
Squealing
One of the most common types of brake pad wear is a high-pitched squeal when braking. This noise is caused by vibration of the brake pad against the rotor. As the brake pads wear down, the vibration can worsen and cause annoying squealing. Factors that can contribute to brake squeal include glazing or hardening of the pad surface, improper pad break-in, and improper pad installation. Squealing is generally more noticeable at lower speeds. While the noise can be irritating, it usually does not indicate any major issues. However, persistent squealing should be addressed to prevent further brake wear and damage.
Grinding
Grinding is a low rumbling or growl sound that occurs when the brake pads have completely worn away, and the metal backing of the brake pad is now coming into contact with the rotor (https://nubrakes.com/blog/brake-grinding/). This indicates that the brake pads are gone and new pads need to be installed immediately. Driving any further with completely worn pads can damage the rotors and brake calipers. Grinding noises tend to occur at all speeds, but are especially noticeable at lower speeds when coming to a stop. The grinding metal-on-metal sound is a clear indicator that the brake pads need to be replaced.
Overheating
Overheating the brake pads and rotors can lead to brake fade, where the brakes lose effectiveness. This often occurs after hard braking, such as when driving downhill for extended periods of time. Excessive heat builds up in the brake pads and rotors, causing the brake material to lose friction. According to the Driver Knowledge site, “The pads are built to work up to a certain temperature. They tend to increase in effectiveness as they get warm, but above a certain point, they’ll start to fade.”
As the brakes overheat and fade, you may notice the brake pedal feels soft or spongy and needs to be pressed further to slow the vehicle. There may also be a burning smell from the hot brakes and rotors. Allowing the brakes to cool down can help restore normal braking power. Severely overheated brakes may glaze the pads and rotors, reducing braking effectiveness until the contaminated surfaces are replaced. It’s important to avoid excessive brake heat through proper driving techniques and maintain the brake system to prevent overheating issues.
Conclusion
In summary, there are several common types of brake pad wear and damage to look out for. Normal wear is expected as brake pads are used, but uneven wear, glazing, cracking, chipping, squealing, grinding, and overheating can indicate problems with the brake pads or other brake components.
It’s important to regularly inspect brake pads, at least every 6 months or 15,000 miles, and replace them once they reach the minimum thickness. Allowing brake pads to wear too thin can reduce braking power and lead to damage of rotors and calipers. Replacing pads before they are completely worn out can prevent more extensive repairs and help keep your braking system in top condition.