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What Are Slotted Rotors and Do You Need Them?

New car rotors. Slotted rotors can improve a vehicle's performance, but not every driver would benefit from them.

Unless you’re driving a high-end sports car, your car’s brake system is mostly likely equipped with blank brake rotors. Also called smooth or plain rotors, blank rotors work well for most of the driving population, so there’s little reason for most drivers to consider anything else, like slotted rotors. So, what are slotted rotors good for?

For most drivers, blank rotors offer the right mix of braking efficiency and thermal efficiency. If you’re a spirited driver, spend weekends at the track, or tow or haul regularly, slotted rotors can be an improvement. Most slotted rotors feature straight grooves crossing the brake pad path, usually at a tangent to the hub circle. Some slotted rotors also feature curved grooves.

Energy Conversion in the Brake System

The brake system is an energy conversion device. Using friction, the brakes convert kinetic energy (the momentum of your vehicle) into thermal energy (heat), which is absorbed by the brake pads and rotors. The heat eventually radiates to the air or is conducted to other parts of the vehicle, like the wheels, axles, bearings and knuckles. For the average driver, automakers build brake systems to handle a certain amount of heat, how much can be absorbed by the system and how fast it dissipates.

  • Heat Absorption: Because 70% of braking occurs in the vehicle’s front end, front brakes are heavier than rear brakes, enabling them to absorb more heat. Rear brakes don’t need to absorb as much heat, so solid rear rotors are still common on many vehicles. Some use old-style rear drum brakes for that reason.
  • Heat Dissipation: To dissipate heat faster, most vehicles are equipped with ventilated front rotors, using airflow to transfer heat to the air. For even more heat dissipation, heavy vehicles, sports cars and work trucks may also be equipped with ventilated rear rotors.

What Are Slotted Rotors’ Advantages and Disadvantages?

Slotted rotors offer distinct benefits over blank rotors, but do have a couple of drawbacks.Slotted rotors are superior to blank rotors in some ways. Slotted rotor grooves offer two distinct benefits under heavy braking: brake fade, from high-temperature brake pad outgassing, can be significantly reduced, allowing gases to escape through the slots; and the grooves shave off thin layers of brake pad material, reducing glazing and improving braking consistency.

Still, slotted rotors have some disadvantages. Depending on the type of grooving, noises and vibrations are par for the course. The brakes are functioning properly, but their aggressive nature may be off-putting to some drivers. And because of the constant shaving action, brake pad life may be shorter than if they were mated with blank rotors. You may also have a hard time finding someone to machine slotted rotors, even if they’re thick enough to resurface. Some urban legends die hard — they’re just not as forgiving as blank rotors.

Slotted rotors are available for many vehicle types, even economy vehicles. If you’re hard on your brakes and you can stand to give up a little comfort and longevity, slotted brakes could be your ticket to better braking.

Check out all the brake system parts and accessories available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on slotted rotors, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Image via Flickr.

Benjamin Jerew View All

Ben has been taking things apart since he was 5, and putting them back together again since he was 8. After dabbling in DIY repairs at home and on the farm, he found his calling in the CGCC Automobile Repair program. After he held his ASE CMAT for 10 years, Ben decided he needed a change. Now, he writes on automotive topics across the web and around the world, including new automotive technology, transportation legislation, emissions, fuel economy and auto repair.

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