What is Brake Pad?
Brake pads are a component of disc brakes used in automotive and other applications. Brake pads are composed of steel backing plates with friction material bound to the surface that faces the disc brake rotors.
Brake pads convert the kinetic energy of a vehicle to thermal energy through friction. Two brake pads are contained in the brake with their friction surfaces facing the rotor. When the brakes are hydraulically applied, the caliper clamps or squeezes the two pads together onto the spinning rotor to slow and stop the vehicle.
When a brake pad heats up due to contact with the rotor, it transfers small amounts of its friction material onto the disc, leaving a dull grey coating on it. The brake pad and disc (both now having the friction material), then “stick” to each other, providing the friction that stops the vehicle.
In disc brakes, there are usually two brake pads per disc rotor. These are held in place and actuated by a caliper affixed to the wheel hub or suspension upright. Racing calipers, however, can utilize up to six pads, with varying frictional properties in a staggered pattern for optimum performance.
Types of Brake Pads
There are four types of brake pads:
- Non-asbestos organic (NAO),
- Low-metallic NAO,
Based on the names of the different types of brake pads, it isn’t apparent which ones are the most widely used or which one you should choose. Here is a rundown of the differences:
- Semi-Metallic. These brake pads are 30 to 65 percent metal and are considered to be very durable. These brake pads may also not function well in extreme, low temperatures. These brake pads are less expensive and easier on the rotors than ceramic brake pads, but that they are louder and do not last as long as ceramics. These brake pads are generally used on high performance and race cars.
- Ceramic. These brake pads are generally the most expensive, but are cleaner and produce less noise than other materials. Ceramic brake pads last longer than semi-metallics as well and ceramics outperform organic pads.
- Low-Metallic, Non-Asbestos Organic (NAO). These brake pads are known to be noisy and to let off a lot of brake dust. However, the copper or steel that is used in these pads helps with heat transfer and breaking.
- Non-Asbestos Organic. These brake pads are generally made from organic materials including fiber, glass, rubber, and Kevlar. These pads are pretty quiet, but can wear faster and produce a lot of brake dust.
Many cars come off of the assembly line with organic pads. This may be because this type of pad is typical for street driving. Although organic brake pads seem to do the trick, you may upgrade to ceramic brake pads if you want less noise and dust. Trucks and SUVs may need brake pads that have more metal for additional stopping power.
Ceramic Vs. Metallic Vs. Organic Brake Pads: Which Is Right for You?
So which brake pad is the best choice for you between ceramic vs. semi metallic vs. organic brake pads? It depends on your vehicle manufacturer recommendations and the ride you expect from your vehicle combined with your driving style.
If you have a high-performance sports car, or at least drive your vehicle like one, you’re likely better off choosing semi-metallic brake pads. On the other hand, if you do a lot of urban commuting, you might find a solid ceramic brake pad to be the better option. If you don’t put a lot of mileage on your vehicle, an organic brake pad might be the best, low-price option for your driving habits.
No matter which types you choose, have your brakes inspected and your brake pads replaced regularly. You’ll know your brake pads need replacement when you hear the squeal of the metal “tang” at the base of the pad as it comes into contact with the rotor.
Tangs are built into all types of brake pads as an indicator of wear; if you hear it, don’t wait too long to get new pads. At that point, deciding between ceramic vs. metallic brake pads or organic pads for a price-friendly option is up to you.
When To Replace Your Brake Pads or What Happens When Brake Pads/Shoes Wear Out?
Every time you engage your vehicle’s brakes, a small amount of friction material is worn off the pads and/or shoes. Over time, the friction material will become thinner. If the pads or shoes are not replaced, the friction material will be worn off entirely, exposing the steel pieces that held the material.
When these steel pieces come into contact with the discs or drums, excessively long braking distances and damage to the discs and drums will result. Look for these signs to know when to replace brake pads or shoes:
1. Squealing or Screeching Noises
If a vehicle’s brake pads have wear indicators, a driver may notice a squealing, screeching or whining noise when the brakes are engaged. This sound is caused by a small metal attachment on the brake pad backing plate for just this purpose.
Wear indicators work on the same principle as dragging fingernails across a chalkboard. When you hear it regularly while braking, it’s time to bring your car to a brake specialist for an inspection. Note that not all brake pads come with this feature, so don’t rely on sound alone to assess your brakes’ condition.
When brakes are exposed to wet, damp conditions, such as after a rainstorm, pads may exhibit a very similar screeching sound while braking. If a sound disappears after the first few times you use your brakes, that’s a good indicator that it was just a bit of moisture on the brake pads or shoes and not a sign they need to be replaced.
2. Less Than a Quarter Inch of Brake Pad
On disc brakes, you can also visually inspect your brake pads to know if it’s time to have them replaced, though it may require you to remove the wheels to do this. Looking down on the brake assembly or “caliper” holding the brake pads, you should see your brake pads compressed against your brake rotor.
If the friction material on the pad or shoe is less than ¼ inch thick (about seven millimeters), consider having your brakes inspected, especially if it’s been a long time since your last inspection.
3. Deep Metallic Grinding and Growling
If you hear a deep, low noise that sounds like metal grinding or a rumbling growl, that can be a sign that not only are your brake pads worn away but also your brake pads or shoes’ backing plates are making contact with the discs or drums.
Since this metal-on-metal contact can very quickly cause even further damage to your braking system, bring your vehicle into a service shop as soon as possible if you hear this type of noise.
4. Indicator Lights
Some vehicles have an indicator light on the dashboard that will signal when it’s time to replace the brake pads. Check your owner’s manual to see if your vehicle comes equipped with a low-pad warning system. Remember that if the light does come on, you’ll need to have your mechanic replace the warning sensors as well as the brake pads.
How Long Do Brake Pads and Shoes Last?
The real answer to how long brake pads and shoes can last will vary from vehicle to vehicle and from driver to driver. For example, if you tend to drive the most often in urban areas or in heavy commuter traffic, you’ll be engaging your brakes a lot more frequently than someone who drives in rural locations or on highways.
Some people also tend to “ride the brake,” meaning they press and depress their brakes more habitually than other drivers, causing the brake pads to wear away more quickly. Brake pads and shoes are generally thought to be good between 30,000-35,000 miles in urban use. In less demanding situations like highway driving in light traffic, brakes may last 80,000 miles or more.