How Brake Rotors Work - Guide [2023]

What are brake rotors?

Of the many crucial systems present in vehicles, the brake system is of particular importance because it affords occupants the ability to stop once in motion. The brake rotor is the rotating part of the disc brake assembly of a wheel. This central braking component is what the brake pads clamp down on to stop the wheels from spinning.

Brake rotors are the circular plane that rotates in conjunction with the axle of a vehicle. Brake rotors convert the motion of a vehicle, its kinetic energy, into heat, thermal energy. Most brake rotors are fabricated of metal, typically gray iron.

They are also called brake discs and you should check out the well-detailed article. In more professional settings, you could find rotors made of exotic materials like carbon fiber.

How do brake rotors work?

Brake rotor mechanism

How do the brakes reduce the speed of a vehicle or bring it to a stop? A moving automobile has a certain amount of kinetic energy. The brakes have to remove this energy to slow it down. Each time you stop your vehicle, the brakes convert the kinetic energy to heat generated by the friction between the pads and the rotor.

When the brakes are applied, brake pads squeezed together by calipers pinch on the rotor creating enough friction to resist the wheel spinning, slowing down the vehicle.

The rotor works the same way in all vehicles. When you press the brake lever of a bicycle, it pulls a metal string squeezing two calipers together, creating friction between the rubber pads and the metal rim on the tire. In a disc brake system, the brake pads squeeze the rotor instead of the wheel, transmitting the force hydraulically instead of through a cable.

Friction between the brake pads and the rotor slows the car down. When the driver presses the brake pedal in a car, a piston inside the brake master cylinder pressurizes hydraulic fluid in the brake lines, which moves the pistons and pushes the pads into the rotor.

The harder the driver presses on the pedal, the harder the rotor gets squeezed. This sequence of events slows down the vehicle and could bring it to an eventual stop. Various brake rotor designs exist for different vehicle types depending on their weight and performance.

Most modern cars have brake rotors on the front wheels, and some high-performance automobiles have brake rotors on all four wheels.

What types of brake rotors are there?

Some brake rotors could be flat and smooth, while others have vents with fins or vanes. This "ventilated" design helps to dissipate the heat generated when stopping a vehicle. A combination of different vehicle size, weight, and speed with more stringent safety standards necessitates the need for different types of brake rotors. To learn more about them, keep reading.

Blank & Smooth

Brake rotors - Blank and smooth

Blank and smooth rotors feature a flat, blank metal surface all around. Its basic design features a flat, level disc, usually made of iron, attached to the rotating axle spindle. They possess excellent braking power due to the large surface area in contact with the brake pads.

This rotor type provides for effective heat dissipation. Blank and smooth rotors offer excellent performance for your daily driving needs, although not ideal for aggressive driving or luxury vehicles. They are resistant to cracking over time and are rigid and dependable. Blank rotors are great for high-performance automobiles in conjunction with enhanced brake pads and fluids. Due to their low weight, blank and smooth rotors are in most passenger vehicles, specifically smaller vehicles.

They are also relatively cheap to produce and replace. However, they can lose effectiveness during prolonged braking periods. Heat, gas, and waste friction material can build up and warp the rotor if the heat buildup reaches critical levels.


Drilled Brake rotors

Drilled brake rotors, as the name implies, have holes drilled in them throughout their surface. A rotor riddled with holes may seem counterintuitive, they work for various reasons:

The holes make heat dissipation easier when braking. The second reason is gas buildup. Older brake pads that cause gas to build up between the pad and rotor are remedied with drilled rotors. The last reason is water. For drivers in wetter climes, stopping power is maintained should the drilled rotors get wet.

The holes allow water, gas, dust, and heat to dissipate faster off the rotor surface, keeping the brake performance optimal. They further enhance pad-rotor contact and offer noted aesthetic value. They also reduce the weight of the rotors via the drilled-out material.

The downside of using drilled rotors is that the holes reduce the amount of heat the rotor can tolerate once it exceeds the amount it can effectively dissipate. After repeated stressful driving, the workload can warp or crack the rotors. Drilled rotors fail pretty quickly in high-performance settings.


Slotted Brake rotors

Slotted rotors feature slots or grooves in the surface of the rotor. These rotors draw in more air between the pad and rotor surface, which improves cooling and heat dispersion. They remove excess brake debris and pad glaze that can occur at higher temperatures. They are ideal for heavy-duty vehicles that need more stopping power when towing or hauling.

Adding slots or grooves to a rotor works in a similar way to drilled rotors. You can think of them as irrigation ditches that move unwanted materials safely out of the way. Without weakening the heat resistance of the rotor, the grooves remove these materials from the friction surface.

They radiate out from the rotor center at a particular angle to vent the waste out and away with the rotor's rotation. Slotted brake rotors are great for performance cars because they put a lot of stress on the rotors. They tend to be more durable than drilled rotors when repeatedly driven hard. The main downside of slotted rotors is that they are noisier than other rotor types.

Drilled & Slotted

Drilled and Slotted Brake rotors

Drilled and slotted rotors combine the drilled holes and slots for enhanced performance. The presence of slots and holes amplifies the benefits of both features while minimizing their disadvantages. Fewer holes mean better maintenance of heat resistance while expelling waste.

A reduction in the number of slots reduces the noise generated when braking while allowing pads to be scrubbed and renewed. Manufacturers designed this type of rotor primarily for performance vehicles that need enhanced cooling and heat dispersion.

The design improves braking at high speeds during racing or track days. Drilled and slotted rotors offer excellent overall behavior during heavy-duty use. They are esteemed when mated with high-viscosity fluids such as DOT 3 or 4.

Recommended read: Brake Disc: How it Works, Types, Problems, and Latest Prices,
How Much Does It Cost To Replace Brake Pads and Rotors: Front & Rear,
Brake linings - an overview (2023),
Brake caliper covers: 2023 Guide

What is rotor warping?

Rotor wraping

Due to the massive amounts of heat, the brake rotor has to deal with, its surface could become uneven over time. This unevenness is known as rotor warping and can cause your vehicle's brakes to become jittery and less effective. Below are the ways a rotor could become warped:

  • When brake pads get very hot due to driving and braking, the pad material can get soft and "paint" the brake rotors. We say the rotor has become glazed with materials from the brake pad. The rotor surface becomes uneven as a consequence, brake efficiency reduces.
  • If you repeatedly ride your brakes while driving, the heat created causes the rotor surface to wear down in certain spots. With excessive heat, the rotor's metal surface becomes soft enough for the pad to wear down the rotor surface. The unworn parts stick out, causing warping.
  • If a newly installed wheel is not properly torqued, there is added stress on the brake rotor causing a warped surface.

Any one of these problems can lead to excessive heating that warps your rotor, especially if they are thin from wear. Generally, the metal of the rotor surface is usually sturdier than the material of the brake pad applying friction to it, consequently, rotors mostly remain unaffected as pads wear down.

How do I know if my brake rotors are warped?

If your rotors get warped, you may notice one or more of the following:

  • You may hear excessive squeaking when the brakes are applied.
  • You may smell burning rubber when braking.
  • Braking is jittery and inconsistent.
  • The vehicle vibrates when coming to a stop.

How do I prevent rotor warping?

To prevent your brake rotor from warping, you have to be mindful of your braking habits. When you repeatedly press on the brakes or hold them down for an extended period, you can cause excessive heat that can warp the rotor surface. Also, be mindful of how much braking the vehicle is doing compared to its regular operation.

When going downhill for prolonged amounts of time, try to control the vehicle's speed by shifting the transmission into a lower gear. For automatics, the only option is to select "3" to keep the engine within the 1st and 3rd gears.

In a more modern automatic transmission, the L setting typically holds the lower gears. Never sit with the brake pedal hard down on one spot when the brakes are hot. Be sure to avoid hard braking when the brake rotors have gotten hot from prolonged use. Also, make sure to break in newly installed brake pads to ensure they do not leave too much material on the brake rotor.

What else do I need to know about brake rotors?

Generally speaking, brake rotors should be checked, replaced, or at least turned every 30,000 to 70,000 miles. The average life span of brake rotors depends on the vehicle and your driving habits. Watch out for noisy brakes, unusual vibrations, visible scuffing on the rotor, or just general reduced stopping power. These could be indications of impending rotor problems. You can read about how to change your faulty brake rotors here.

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