All You Need to Know About BMW Brakes & Brake Pads

Don’t you just like driving really, really fast sometimes? We all do! But it’s one thing being able to accelerate quickly and to great speeds, and another coming to a stop after you’re done having fun. Luckily, that’s why there are brakes in our BMW cars. This and the ability to tailgate them slowpokes on the highway, which requires utmost precision in speed control.  

Today, we’re going to take a closer look at the technicalities behind the BMW brake systems: the BMW brake pads, BMW brake rotors (or discs, if you will), and everything else that makes them up. We will also debunk some brake service myths – but that story will continue another time!

Coming up: 

• What are the parts of a (not only) BMW brake system?
  
• What are the most common issues with BMW brakes?
  
• How many types of BMW brake pads & rotors are there?
  
• When should you service your BMW brakes?

Read on to learn more!

What Makes Up the BMW Brake System and How Does It Work?

Possibly one of the most important safety features of all cars, modern-day BMW brake systems are a result of continuous improvement efforts over a few decades. While the general principle of operation is the same as it was many years ago, some new components were added along the way. But let’s take a small step back. 

What exactly happens when you press on the brake pedal? 

Connected to it via a pushrod is a device called the master cylinder. Within its housing, there are a couple of circuits, each consisting of return springs, seals, as well as ports for intake, return, and equalization. These are the openings that allow the brake fluid to flow from the reservoir placed on top of the master cylinder body. 

Not unlike the one found in clutch systems (any manual drivers still out there?), this master cylinder is meant to convert the force from your foot into hydraulic pressure to operate the slave cylinders. It does sound kind of weird or kinky, but hear me out: the slave cylinders are nothing more than the pistons within the BMW brake calipers. 

Actuating the brake pedal either closes (pressing it down) or opens (releasing it) the appropriate ports and builds up the required pressure. This pressure then flows through the brake lines and into the pistons, making them push BMW brake pads against the brake discs, hence creating friction and stopping their rotation. And the vehicle in the process. 

Here’s a cheat sheet of what it goes like:

1. You depress the brake pedal.
2. The pressure in the master cylinder builds up.
3. From there, the pressure travels through the brake lines.
4. Then it gets to the slave cylinders, i.e., the pistons in the BMW brake calipers.
5. Your car decelerates and comes to a stop (hopefully).

Sounds pretty straightforward, doesn’t it? 

Well, there is one problem though: repeatedly pressing the brake pedal and exerting enough force on it to stop the car can get really exhausting really fast. So while this system is basically bulletproof in terms of reliability, its main downside is that the only thing multiplying the energy from your foot is the leverage of the brake pedal. 

This is more than fine for lightweight cars, but the more mass—including the rotational mass from BMW brake discs, wheels, and tires—the more force is required to stop. With modern cars weighing in excess of 3,500–4,500 lbs (1,600–2,000 kg), I think you can see how this could become a pretty big inconvenience, especially during everyday commutes. 

After all, your 3 Series is meant to help you get from point A to B, not make you work out by maniacally pumping on its BMW brakes, right? Luckily, at some point in car development history, someone decided to remedy this issue by slapping on a particular component. That’s how the power-assisted braking system was born.

Power Brakes vs. Manual Brakes – What’s the Difference?

You see, their solution to this issue was quite elegant, in that it’s actually very simple and does not use any complicated parts. Between the brake pedal and master cylinder, they just added a vacuum servo, now commonly known as a brake booster. Without getting into too much technical detail, this part greatly multiplies the force applied to the brake pedal. 

How? Using the pressure difference between the two sides of the brake booster. On one end there is the vacuum supplied by the running engine. On the other, the atmosphere and the air let in through a special valve. This pulls on the booster’s inner diaphragm, which is connected to the pushrod that goes into the master cylinder – and that’s where the assistance comes from.

Before some of you ask “But why is there a vacuum in the engine?”, here’s a quick automotive physics reminder. On the intake stroke of the combustion cycle, the piston moves down within the cylinder. Since the combustion chamber is empty at that point, a vacuum is created that extends into the intake manifold and sucks the air into the chamber. And the brake booster simply “borrows” some of that vacuum for the purposes of brake assistance. There, that’s it.

If you’d like to learn more about the combustion cycle itself (or other factors that affect it), make sure to check out our article about Types of Gas for BMW Cars. There, we touch on a lot of subjects that might interest someone who likes to get technical.

Now back to the BMW brakes…

Overview of BMW Brake Pads and BMW Brake Rotors

You probably already know this, but BMW brake pads and BMW brake rotors are exactly the same as the ones you can find in other cars. Of course, the materials used in them will vary depending on the manufacturer, however, they are principally the same. Before we dive deeper into rotors and pads, there is just one thing that needs explaining.

BMW Brake Rotors

OEM BMW brake rotors (or BMW brake discs, if you will), are usually made of metal. Although in the highest-performance applications, you will often find BMW carbon ceramic brakes, manufactured using special ceramic composites. In the case of ventilated brake rotors, they consist of two discs joined together with directional fins sandwiched between them that help to cool down the interior of the rotor. 

One other thing worth noting about BMW brake rotors is their size in most applications. 

As you might have noticed when passing some parked vehicles, usually the front brake discs are bigger than the rear ones. This is meant to overcome the shift of weight that happens when braking – as the nose of your car dips down, more force is applied to the front axle. 

Consequently, the front wheels are getting more traction, which is why the front BMW brakes have more work to do. Which is why the manufacturers make them bigger. This is a very oversimplified description, so if you want to learn more, check out the video linked below. It explains the subject in great detail, but also in a clear and concise way. 

What you could’ve also noticed on many “sporty” street cars are tiny little holes drilled into the surface of a rotor. Or, if you’ve been particularly lucky, with small rows all around. Since they are used on performance-oriented vehicles, they must have some purpose, right? Right…? 

Drilled vs. Slotted BMW Brake Rotors

Yes, they do have a purpose. 

The design of BMW brake rotors with holes, a.k.a. drilled brake discs, comes from an era of brake pads manufactured from asbestos. Compared to their modern counterparts, they had a tendency to emit more gasses, which got trapped between the pads and the rotor surface. To remedy this, holes were drilled into the rotors, allowing the gasses to escape more freely. 

This flow of gasses has one additional advantage, namely heat reduction. If the brake rotors are both ventilated and drilled, the air in the vanes can get out not only from the top (the opening between two discs) but also through the drilled holes. As a result, the brakes cool down faster and are less susceptible to brake fade.

Small cuts on the surface are another type of “cosmetic” enhancement on brake rotors. Slotted brake discs, because that’s what they are actually called, fulfill a similar purpose to the drilled ones. They help remove gas and dust, preventing it from getting stuck between pads and rotors, therefore allowing for better contact and more stopping power. Additionally, since the pad has to go over the edges of the slots, such configuration allows for a better “bite,” i.e., sharper brake pedal reaction. 

At the same time, slotted BMW brake rotors have slightly worse heat transfer than drilled ones. And in some cases, the drill holes affect the longevity of the discs – there is less material, so they naturally wear off faster. This is why in serious motorsport applications, you are more likely to see either slotted or just plain solid brake rotors. 

BMW Brake Pads

When it comes to brake pads, there are even more possibilities. As a rule of thumb though, each of the available options has its own set of optimal applications – there just isn’t one that would be perfect for everything. A few main types of BMW brake pads exist:

• Non-metallic (organic) brake pads
• Semi-metallic brake pads
• Fully metallic brake pads
• Ceramic brake pads

I’ll explain what’s what in just a bit, but let’s just quickly discuss their limitations. 

So, if we take for example the regular semi-metallic BMW brake pads, we get something that will last quite a long time and provide a very good stopping power. For some additional brake fade resistance on track, you’d grab performance-oriented brake pads with lower metal contents. 

On the other hand, if you are after a cleaner look, ceramic brake pads are probably your best bet. They do not produce as much brake dust as semi-metallic or organic brake pads. While they offer good stopping performance, they are not as fade-resistant as the semi-metallic ones. The main issue is that they simply get hotter and transfer the heat onto other parts of the braking system.

Below is a table with a quick little breakdown for your convenience.

Now that we covered the basics, let’s get to clearing up some confusing BMW brakes marketing mumbo-jumbo. Because they do that a lot, like with everything – luckily, the information is available out there, even though it’s slightly hidden.

Types of BMW Brakes – Regular, BMW M Sport Brakes, or What…?

As mentioned above, the naming conventions used by BMW can sometimes be confusing. Or outright pointless. This is why the best way to differentiate between all the available BMW brake systems is the rotor size. 

For example: in the BMW 3 Series (F3x and G2x) and BMW 2 Series (F2x), you could option in either the M Performance Brakes or M Sport Brakes. With the BMW M Performance Brakes, the situation is pretty simple – they always came with 14.6” (370 mm) front and 13.6” (345 mm) rear rotors. 

However, the BMW M Sport Brakes are a different story. Their front rotors differ in size depending on the car model they are installed in. These can have a diameter of 14.6” (370 mm) or 13.4” (340 mm), while the rear ones are the same as in the M Performance Brakes (yup, weirdly enough, the rear gets bigger discs!). Both packages also use 4-piston front BMW brake calipers from Brembo, albeit of slightly different sizes (if different-size rotors are used).

Still confused? Let me break it down even further.

• The BMW M Sport Brakes – rotors can be bigger than regular, although in many cases they are smaller than the M Performance ones and have a smooth surface; come with 4-piston front brake calipers (their size depends on the rotor diameter).
• The BMW M Performance Brakes – these always have the biggest possible brake rotors that can be additionally slotted and/or dimpled; also come with 4-piston front brake calipers by Brembo.

I hope now you get a general idea of what sets the two apart. It’s so difficult to classify all these systems because BMW doesn’t really provide information about them in spec sheets or on their website. The info is there somewhere, but apart from lifting your car up and taking a look at the backside of the BMW brake caliper, there really isn’t a sure-shot way of verifying that.

Amidst all that confusion, there is one BMW brake system that stands out and is quite easy to spot without much hassle. These are the BMW Carbon Ceramic Brakes found on the top-of-the-line M cars, not just the M-style trims. 

A Word About the BMW Carbon Ceramic Brakes

Don’t be fooled by the “ceramic” in its name. While ceramic BMW brake pads are meant primarily as a way to reduce brake dust emissions and still provide optimal stopping power, BMW Carbon Ceramic Brakes are a different story. A story strictly about the highest possible performance.

These systems come with beefier, multi-piston BMW brake calipers, highly efficient brake pads, and special BMW brake rotors. The brake rotors are made of carbon ceramic composite drilled discs with a lightweight centerpiece (called bell or hat) bolted right onto them. This type of brake disc design is called two-piece or floating. 

BMW Carbon Ceramic Brake systems offer better… well, everything. Apart from the price, but I’ll get back to that in a bit. Although the brake calipers are slightly heavier than the stock ones due to more pistons and overall more robust build, the BMW brake rotors save a lot of weight. Depending on the BMW, you’re looking at savings of 18 lbs (in cars like the BMW M3) to 42 lbs (in the likes of the BMW M5).

Ceramic brakes also prefer to work in slightly higher temperatures than their semi-metallic counterparts. Of course, they will stop you with no problem even if they aren’t warmed up. But they shine the most at really high temperatures, where their extreme fade resistance outmatches even performance-oriented metallic rotors. 

Their biggest downside is that they cost an arm and a leg. Really, this option can cost over 15 thousand dollars! You could get a used BMW 550i from 2015 with around 100,000 miles on the clock for this much money… then again you wouldn’t track it, would you?

Basic BMW Brake Maintenance

Having covered so much theory, let’s talk about something more practical – BMW maintenance. It’s no rocket science: brake pads and rotors, as well as the brake fluid, are all parts that should be periodically replaced. I guess you already know that. But do you know what are the recommended service intervals for each of those? 

A good practice is to replace:

• BMW brake pads – at either 15,000–25,000 miles (heavy use, dynamic driving style) or 40,000–50,000 miles (e.g., lots of calm highway driving); no later than at 3–5 mm of pad thickness.
• BMW brake rotors – usually around twice as much distance as a set of brake pads, so in the ballpark of 50,000–75,000 miles; when both sides of the braking surface are worn by around 0.5 mm (rear) and 1 mm (front).
• BMW brake fluid – every 2 years or 30,000 miles for regular usage; if you drive very spiritedly a lot, you should cut that interval in half to 1 year or 15,000 miles (whichever comes first).

Note that these are all “rule of thumb” types of figures and, as such, should be treated more like suggestions. What also affects the longevity of brake system components is the atmospheric conditions and the type of transmission used by the car. Automatics tend to wear brake pads and rotors more than manuals. 

It’s always best to have your pads and rotors inspected by a qualified mechanic when visiting the service shop or your dealership. We will discuss the subject of BMW brake service and common issues with BMW brakes in another article.

Safety First! OEM Replacement BMW Brakes

Regardless of the brake system installed in your BMW, it’s best to pay attention to any noises coming from your wheels during braking or the behavior of your brake pedal and steering wheel. And when the time comes for BMW brake replacement, using OEM BMW Brake Pads and BMW Brake Rotors is the way to go. 

While the level of performance will be the same as with the stock brakes, you’ll get the certainty of the manufacturer's warranty for any potential production defects. If you’d like to upgrade to some high-performance parts, but your car is still new and under warranty, you should consult your dealer about any modifications. 

PS We also offer BMW brake pads and rotors for other models, not only the F3x linked above. If you can’t find it on our site, reach out to our sales team – they’ll be able to help you choose the suitable parts for your car model.