Nov 27

Tech Tuesday: Disc Brakes

Another Tuesday another day to discuss the tech that goes into your cars. Today’s topic at hand is something not a whole lot of people think about until it comes time to replace them and that is brakes. Specifically disc brakes today. It seems simple, but there are all kinds of designs, materials, and things to consider if you are upgrading your discs so hit the jump and let’s dive into this a bit more.

Disc brakes operate quite simply, they use a caliper with a piston in it to push brake pads up against the disc. This action creates friction and thus slows down the disc (rotor) which is attached to the axle via a hub and a tire slowing the car down.

According to Wikipedia the first disc brake was patented in 1902 and used on Lanchester cars so the technology isn’t exactly new. As it stands today disc brakes are pretty much standard on everything. This is largely because of their ease of service, consistent feel, and reliability. Of course disc brakes are found on just about everything from cars, trucks, and even bicycles.

Advance Auto Parts - Keep the Wheels Turning

Your standard disc will be made of cast iron. On an application that will require little heat dissipation the disc will be solid. However on applications where heavy braking may be expected such as racing or towing applications the disc will often have vents and fins between the two rotor surfaces to shed heat.

Cross drilling is a popular method of dissipating heat on high performance applications. This was particularly true in the 1960s and 1970s as well as today. However modern race applications do not use the cross drilling method because the potential for cracking of the rotor in high stress situations.

drilled rotor

Slotted rotors are another option for disc brakes. It is often thought that slotteed rotors are made for heat dissipation but that is incorrect. Slotted rotors are made for deglazing and wet performance. Deglazing is needed in situations where pad material can sometimes build on the rotor in a glaze, the slots help remove that material. The slots do the same to water and other debris that can hinder performance. Slotted rotors are most commonly found on race applications as they provide maximum performance at the cost of decreased pad life.

While drilled and slotted rotors can often be found on modified street cars the combination is not good for performance due to the increased risk of stress cracking and pad wear. When I’m consulted on which rotors to choose I never recommend a drilled and slotted rotor.

As previously mentioned the most common type of rotor is cast iron. This is because they are cheap and durable to make in a mass production setting. However starting in the mid 1970s race cars began to use a Reinforced-Carbon disc to save weight. Unsprung weight is the enemy of a race car and as composite technology became available it was only a matter of time before race teams used it. Today most top flight race teams use a Carbon-Carbon disc.

Modern high end street cars use a ceramic disc to help improve performance and reduce weight. They also significantly reduce dust and lower mainteneance intervals. This technology is readily available on the aftermarket at a pretty reasonable price for nearly any sporty application.

So as you can see disc brakes are pretty simple but with quite a few options for varying applications. Hopefully we cleared up a little bit of it today. We’ll talk about more brake components in a later tech Tuesday article.

Photo Sources:
Mercedes Benz