Table of Contents
- What are Brake Pads?
- How Does a Disc Brake System Work?
- How are Brake Pads Made?
- Why Do My Brake Pads Need Replacing?
- How Can I Make My Brakes Last as Long as Possible?
- How Do I Know That My Pads Need Replacing?
- Other Potential Problems With the Brakes
- Should I Change Both My Rotors and Pads? Or Just the Pads?
- How Much will Getting Some New Rotors and Pads Cost?
Brake pads are just one of those things you’re never going to hear the end of. It’s one of the fastest-wearing parts in your car; before you know it, you’ll be needing some new ones.
In this article, we’ll go through how brake pads are built, how much you should expect to pay for a new set, and some general maintenance advice.
As you read through this article, we hope that it’ll be useful for you and that you can apply this knowledge the next time your brakes begin to wear out.
What are Brake Pads?
Most cars nowadays use a type of brake called a “disc brake.” Disc brakes work by using much the same principle as the brakes on a bicycle. When you press the pedal, frictional materials are pressed firmly against a rotating material fixed onto the wheel.
This frictional force produces a lot of heat. Technically, this is a reaction converting rotational energy into heat energy. As the rotational energy gets removed, the wheels don’t turn as quickly. They decelerate. As the wheels are the contact point of the car with the road, this, in turn, slows the car down.
In cars, the frictional force is applied using what’s known as brake pads. The brake pads press onto the brake disc’s front and rear faces, which is also commonly called a rotor. This brake disc is fixed onto the wheel bearing, so as its rotational speed slows down, the wheel slows down.
You’ll always find brake pads in the “disc brake” system. The other type of brakes commonly used on cars is the “drum brake” system. Without going into this system in too much detail, you’ll find that drum brakes offer far less in terms of “stopping power,” but they are easy to attach a cable to, which allows you to apply them manually. This principle is applied in most cars with a manual handbrake. When you pull the handbrake, the drum brakes are activated. In almost every modern car in the world, these drum brakes will only be at the rear.
On the newest cars, most will have disc brakes on all four wheels. Instead of a handbrake, you’ll find an electronic parking brake. When you pull this, an electrical signal is sent to the brakes to press the pads into the disc. In that way, it functions in the same way as a handbrake. This system is different from the handbrake in that you can’t pull it while you’re moving. This makes little difference to most people, but it won’t be long before handbrake turns are only possible on what will eventually be termed “classic cars.”
How Does a Disc Brake System Work?
Let’s delve into disc brakes in a little more detail.
The braking system in almost every car is hydraulic. Hydraulic systems have been tried and tested for many years and are often thought to be the most reliable. All “hydraulic” means is that it’s a system that uses liquids.
In a hydraulic system, the liquid fills almost the entire system. Because fluids are virtually incompressible, when you push the fluid at one end, it moves at the same rate at the other end.
To help you imagine this, think of a syringe. When you press down on the plunger, you know that, depending on how hard you press, water will come out of the end. If you block the end of the syringe off, you will not be able to push the plunger down any further.
When you press the pedal, the brake master cylinder pushes the fluid through the system. The master cylinder acts a bit like the plunger in the syringe. This fluid goes to the brake calipers.
The calipers have a piston (or more) that holds the brake pads and press them against the brake discs. When you release the pedal, the caliper piston(s) also relaxes, pulling the brake pads away from the discs.
This is, in very basic terms, how a car slows down when you apply the brake pedal. Engine braking is also used. This is the engine’s frictional forces helping to naturally decrease its rev-rate as you remove your foot from the gas pedal.
How are Brake Pads Made?
Brake pads today are generally made of metal. At least, they will be mostly made of metal. To keep costs down, manufacturers use alloys and sometimes incorporate trace elements of other materials in.
You’ll usually find metals such as iron, steel, graphite, and copper in brake pads. Copper, however, is slowly being reduced in brake pads in countries around the world. The main reason for this is that copper dust is particularly harmful to the environment. As the copper deteriorates with use and age, the particulates of rust and dust wash away, entering water systems and eco-systems. Over time, this will cause extensive amounts of harm, and so the use of this material is slowly being phased out.
Metals are used in most consumer brake pads for the following reasons:
- Due to metals’ strength and structure, metallic brake pads are durable and last much longer than other contemporaries.
- Metal is an effective material at transferring heat away from the brake discs. This is important because brakes stop working as well when they get too hot – this is called “brake fade.” We’ll touch on this a little more later on in this article.
- There is a huge supply of metal available for manufacturing, so there’s no concern over running out of raw materials any time soon.
- The metal manufacturing industry has been up and running for a long time, so most equipment is easily available, and the processes have been tried, tested, and refined over the many years of the industry.
There are also a couple of disadvantages involved with metal brake pads, although these are reasonably insignificant when it comes to brake pads on most consumer cars. These include:
- Brake pads work most effectively when they are warm on a colder day. It may take a small amount of time for the brake pads to warm up to temperature before they are 100% effective. In most situations, though, this shouldn’t take more than a minute or two.
- Metal is slightly heavier than other materials that might be used in brake pads. This means the car is ever so slightly heavier than it would be otherwise, which technically affects fuel economy and handling. In reality, though, these weights are so minimal that it makes little-to-no difference.
Why Do My Brake Pads Need Replacing?
Brake pads are naturally going to wear out over time. The more harshly the brakes are used, the more forces will be transferred through the brake pads. The more forces are sent through them, the quicker they will wear down.
“Brake fade,” as touched upon earlier, is when you have been braking heavily for an extended period, such as if you have to slam on your brakes when traveling at speed on the highway. As the brakes get hot, they don’t slow the car down quite as effectively, and so it may feel like your car isn’t stopping as quickly as it should.
If this situation does happen to you, simply ease off the brakes slightly for a moment to allow them to cool down.
It could also happen if one of your calipers is stuck, and is constantly compressing the pads against the disc, no matter how slightly. This could be one of the reasons that your brake pads need replacing.
When a brake pad gets worn down, it will eventually not be able to brake the vehicle effectively. Once this has happened, it’s vital to get a new set.
Manufacturers always produce their brake pads with a strip of metal in them towards the bottom. As the brake pads wear down, they eventually reach this strip of metal. When you hear a harsh, squealing sound from your brakes and know that they’ve covered many miles, that’s what that probably is.
These are intentionally designed as an audible signal to let you know that your brake pads are getting low and need to be changed soon. While the car will still be able to brake and stop efficiently, you should make sure you get some new brakes as soon as possible.
How Can I Make My Brakes Last as Long as Possible?
The best way to make your brakes last as long as possible is to brake smoothly and gently. Don’t push the pedal harshly – squeeze and maneuver it. The same principles apply to the throttle and clutch pedals, and steering wheel.
Doing this will put a minimal amount of strain on your brakes, making them last as long as possible.
As well as this, it can’t hurt to visually inspect them now and then, just to make sure everything looks alright.
How Do I Know That My Pads Need Replacing?
Aside from the squealing mentioned above, there are a few other signs that your pads need changing.
Many newer cars are fitted with sensors attached to one of your brake pads (usually the inside one). These sensors read when the pad is getting low and will cause a warning light to appear on your dashboard. A little like the built-in squealing, this one is pretty obvious. When this sign appears on your dashboard, it’s time for some new brakes.
If the car judders a lot when you come to a stop, you’ll probably also feel that your stopping power isn’t what it once was. This is due to the brake pads being unable to apply as much frictional force to the rotor as they could when they were new. Once your car reaches this stage, and the problem is almost certainly the brakes, you should immediately book your car in with your local garage. The brakes need to be changed as soon as possible.
If, when you put the brakes on, the car pulls to either the left or the right, this could also be a sign of brake pads wearing unevenly, especially on the front. The actual fault itself may not rest with the brake pads, but they will need to be changed nevertheless. You should look to the rest of the braking system to find the problem.
It will most likely be something to do with one of the brake calipers (on the side of the more worn pad) or a leak in the brake line (or the side of the less worn pad). Bear in mind, however, that this could also be a sign of a problem somewhere in the steering system, such as the tracking, a puncture, an imbalanced wheel, the steering sensor, the steering rack, or something else.
Finally, a particularly obvious way to check your brake pads is to inspect them visually. On cars with large wheel spokes, you will be able to see down behind the wheel to look at the outer brake pad. Using a torch, shine some light down there so you can see what you’re looking at. If the pads look less than 3 mm, it’ll soon be time to get them replaced.
You can legally drive them for a bit longer than this, but at this point, they’ll begin to stop functioning so effectively. If you can’t see the brake pads because you have steel wheels or thick alloy wheels, simply remove the wheel to take a closer look. Put your eye parallel with the side of the car and look directly at the brake pad to get an accurate measurement. If you’re really unsure, there’s no harm in using a tape measure.
Other Potential Problems With the Brakes
We have just run through a few signs of damaged or worn pads, but you may experience others if another part of the braking system fails.
As we mentioned earlier, if one of your calipers seizes up, the brake pads could not get pushed onto the rotor at all, or they will be constantly stuck on. The latter of these is slightly more common. Either way, you’ll notice uneven wear and braking may feel funny. When a situation arises where the ABS should come on, you may only feel it on one side of the car.
You should also visually inspect your brake discs from time to time. Over time, these may gather some light surface rust and eventually will build up a lip around the edge, which can be a sign of being needed to be replaced.
A more serious problem with brake discs is cracking. Due to the intense forces being put through them, brake rotors can occasionally develop cracks. These will initially only be hairline cracks and will look like a pen mark drawn lightly across the disc’s surface. But it’s a much more serious problem. If you see any evidence of this, take your car to a mechanic to get them to check it out. If it’s something serious, you’ll immediately need a new set of discs and pads.
Brake lines can develop leaks, but you shouldn’t worry too much. Even if this happens, your car is designed specifically to make sure you have as much stopping power as possible. When the brake fluid leaves the master cylinder, it splits into two paths.
One brake line runs from the front right wheel to the rear left. The other runs from the front left to, you guessed it, the rear right. This means that if one of these lines develops a leak, you will still have half of your usual stopping power.
The reason these brake lines don’t run across axles or the sides of the car is to make sure that the braking forces are as balanced as possible. Since the front of the car does most of the braking, if lines were going across the axles and the front brake line failed, the only working brakes would be at the back.
These only provide 40% of the total braking force, as an absolute maximum, and so you would find your stopping power severely diminished. Likewise, if the lines were set down individual sides of the car and one failed, the wheels on one side of the car would lock up when you tried to apply the brakes. This is because of the excessive forces causing you to spin.
There are also more minor problems, such as surface rust and surface water. These will cause your brakes to judder slightly but should wear off with time as you drive.
Should I Change Both My Rotors and Pads? Or Just the Pads?
Most mechanics will recommend that you change both the rotors and the pads. This isn’t just your local money-loving businessman trying to get as much money out of you as possible. It’s important to do.
Although many online forums will let you know that you only have to change the pads, this isn’t the safest thing to do. In fact, many garages may even refuse to do work for you if you only want to change the pads, and they are more than entitled to do so. Your brakes are much more likely not to work properly if you only change the pads. The garage which worked on your brakes may get in trouble if you crash. This is why that situation may or might have arisen for you.
We would always say to change both the rotors and the pads at the same time. Here’s why.
Your brake pads create a groove in the brake rotor as it spins. This groove has been slowly developed over the many miles that you cover per year, and thus it’s very specific to that exact pad. When you install a new pad, it will sit slightly differently and have slightly different minute manufacturer defects. Because it sits slightly differently in the caliper and on the rotor, you’ll find that the flat of the pad doesn’t fully press into the rotor. Because of this, you’ll risk getting barely any braking force at all.
They’ll then also wear at the same rate. You’ll be aware of approximately when you should change them again – probably around every 20,000 to 30,000 miles. If your brakes need replacing sooner than that, you will quickly pick up that there’s probably something wrong with your braking system.
That’s why it’s crucial to change both your rotors and pads at the same time.
How Much will Getting Some New Rotors and Pads Cost?
Getting a new pair of rotors and pads can be quite expensive. You must always get both wheels across the axle done at the same time. How much you should expect to pay will depend on a variety of factors:
- Prices are influenced by the area you live in. Living in a high-end area will result in prices being more inflated than other garages.
- You’ll also pay more for a garage with a stronger reputation for doing a good job than other garages.
- The mechanic may quote you for a few different products – if they don’t, you should ask them to. Ask for a quote on budget rotors and pads, mid-range ones, and high-quality ones. This will give you a good range to pick from, to analyze the pros and cons. Some products will come with warranties and assurances and extra bonuses, so be sure to take them into account.
- The type of car you have will also make a dramatic difference – having an expensive car will undoubtedly lead to more costly part replacements.
For your average car in the United States, we would expect an average price, including fitting, wheel balancing, and labor costs, to be somewhere in the range of $250 – $400. However, all the factors that we have mentioned above will influence that number, so you may pay dramatically more, depending on your make and model and where you live.
If you know your way around the braking system and plan on changing your brakes yourself, great – expect to pay between $130 and $200 for a good set of rotors and pads.
Brake pads are one of the most important parts of your car, and it’s important to keep an eye on them. This ensures that your car is always able to stop efficiently. Look after them and make sure they are in good condition, and they will last as long as possible for you.
We hope this article has been useful for you and that you can use this information to help you as you change out the brakes in your car.