Rust on Brake Rotors Is Easy to Remove

If you’ve just washed your car or left it outside during a rainstorm, you may notice surface rust accumulating on your brake rotors. Is rust on rotors bad for your brakes? Or is it just a minor aesthetic annoyance? 

We’ve got good news for car owners: in most cases, light surface rust on rotors is normal and will go away by simply driving your car. 

When you’re driving and you press the brake pedal, the brake calipers squeeze the brake pads against the rotors, causing the wheels to stop. When the brake pads squeeze against the rotors, they shave rust off of the friction surface. This cleans the rotor surface of rust. 

That’s why rusty rotors are commonly seen on vehicles that have been left to sit for long periods of time. If you aren’t engaging the brake system, rust will continue to build up. This is the reason why you’ll even see rusty rotors on new cars — new cars sit on lots without being driven, so the rust keeps accumulating. 

All that being said, while light surface rust isn’t a problem, there are cases where heavy rust buildup can compromise the structural integrity of your car’s braking system. Cases like these may require you to remove the rotors from the vehicle to properly clean or even get new rotors entirely. 

So what causes rust on rotors, and how do you prevent it from building up? We’ll cover that plus tips for cleaning and maintaining your rotors. 

What Causes Rust on Rotors?

Rust on rotors is caused by iron oxidation. Most rotors are made of iron, such as cast iron or an iron alloy like steel. When iron is exposed to oxygen and water, it forms the flaky orange coating that we all know as rust. Exposure to salt will accelerate that oxidation process. Here are some common scenarios that can lead to rust on rotors:

• Leaving a Car Outside: Exposure to humidity in the air can cause light surface rust to appear.
• Rain Exposure: It’s very common to see rust on rotors after rain due to prolonged exposure to water. 
• Washing Your Car: You may see rust on rotors after washing as the water from the car wash can cause surface rust. 
• Driving in Road Salt: Salt, combined with water from snow and sleet, will accelerate rust buildup. This will happen whether you drive an SUV or a compact — ride height is irrelevant. 
• Not Driving Your Car for Long Periods of Time: As we mentioned in the first paragraph, surface rust on rotors is easily removed by simply driving the vehicle. If you’re not driving for an extended period, rust will develop. 
• Low Quality Rotors: Higher-end cars and aftermarket rotors usually have a rust-proof coating applied that helps prevent rust. Most rotors, however, have a bare metal surface that’s extremely prone to rusting. 

Is Rust on Rotors Bad?

Light surface rust on rotors is not bad. A bit of rust won’t damage your braking system and will go away with regular driving. You don’t need to replace the rotors when it’s just a thin layer of rust. 

Heavy rust buildup, however, can and will damage your brakes, reduce the life of your rotors and potentially put your life at risk. Here are some possible risks from too much rust:

The Dangers of Heavy Rust Buildup on Rotors

Uneven Brake Pad Wear: When heavy rust buildup is neglected, it can cause uneven wear on the brake pads (also known as brake discs in the UK) due to the bumpy texture of a heavily rusted surface. Uneven wear can make brake pads deteriorate more quickly, and if they lose the ability to stop the rotors, your car’s brakes will stop working. 

Rotor Wear Beyond Minimum Thickness Specifications: Every OEM sets a “minimum thickness specification” for their vehicles’ rotors that determines how thick a rotor needs to be for the braking system to function properly. If the rotor is too thin, the brake pads won’t be able to clamp down on the rotor properly and will be unable to brake the vehicle. Heavy rust accelerates rotor wear, eventually removing enough surface material to bring the rotor below minimum thickness specifications. 

How to Get Rid of Rust on Rotors

As we mentioned above, most rust on rotors is light surface rust and can be easily removed by simply driving your car. Follow these steps as part of your general vehicle maintenance. Here’s how it works:

1. In a parking lot or on an empty street, drive car at 7MPH
2. Engage brakes
3. Repeat as needed to remove rotor rust 

But what if that doesn’t do the trick? Some electric vehicles don’t engage the mechanical brakes at low speeds because regeneration (putting charge back into the battery) is slowing the car instead. In cases like these, follow these steps:

1. In a parking lot or on an empty street, shift car into neutral.
2. Press the brake pedal until the car is almost at a complete stop. 
3. Repeat as needed to remove rotor rust.

How to Remove Heavy Rust on Rotors

When rotors are heavily rusted, braking may not be enough to remove the rust. The rust might even be bad enough to make driving the car dangerous — heavy rust on rotors can cause strange noises and pedal vibrations that make driving terrifying. In cases like these, we need to take more aggressive steps to remove rust. Here’s a step-by-step guide for removing heavy rust. 

WARNING: The following instructions require wheel removal and the use of harsh chemicals. If you need assistance, contact the dealership or a reputable body shop near you. 

How to Remove Moderate Rust buildup

1. Lift the front or rear of the vehicle using a jack. 
2. Remove the lug nuts and wheels from the car. 
3. Spray brake cleaner onto the rotor.
4. Using steel wool or a wire brush, agitate the brake cleaner to remove rust. 
5. Rinse. 
6. Let dry before replacing wheels and lug nuts.
7. Repeat on the opposite side of the vehicle. 

How to Remove Heavy Rust buildup

1. Lift the front or rear of the vehicle using a jack. 
2. Remove the lug nuts and wheels from the car. 
3. Submerge rotor in a bath of white vinegar and salt. 
4. Let sit for 12 hours. 
5. Remove rotor from bath and use a steel wool pad or wire brush to remove remaining rust. 
6. Rinse.
7. Let dry before replacing wheels and lug nuts. 

How Do I Prevent Rust on Rotors?

For the most part, rust on rotors isn’t something you necessarily need to prevent. It’s normal for exposed metal to develop light surface rust, and it goes away with driving. That being said, for some, it’s a major aesthetic annoyance that ruins the look of their vehicle. So what do you do if you want rust-free rotors? 

Option #1: Apply a Protective Coating

Applying a protective layer of rust-proof coating is the easiest way to prevent rust on rotors. Here’s how to protect your rotors against rust:

1. Clean your wheel and tire with a wheel cleaner. 
2. Let the chemical sit for 2-3 minutes.
3. Agitate the wheel with a wheel brush and the tire with a tire brush to remove contamination. This will ensure the coating has a clean surface to bond with. 
4. Spray the protective coating over the rotor. Repeat on all wheels.
5. Wash and dry the car.
6. Move the vehicle back and forth and apply the brakes to distribute the coating evenly across the rotor.

Option #2: Buy Coated Aftermarket Rotors

The reason why rotors rust so easily is because vehicle manufacturers forgo the protective coatings and treatments to save money and weight. Aftermarket rotor manufacturers, on the other hand, will typically treat their rotors with a rust-proof coating to help mitigate rust buildup. These coatings may not last forever, but they go a long way towards keeping oxidation at bay. 

Conclusion

The big takeaway here? Rust on rotors is normal and will go away by driving the car in question. You don’t have to worry about removing it or whether it will damage your brake system. That being said, if rust builds-up for too long, it may get to the point where you either need to do a “wheels-off” clean or just have them replaced entirely. 

Whatever the case, hopefully this article helped you properly diagnose your rust issues. Have questions? Comment below and we’ll chime in with an answer!