There’s rust on my brake rotors – Should I worry?

After leaving your car out and exposed to the elements for a bit, you may find that your brake rotors can collect a bit of rust especially after a rainstorm or after you wash your car. In many cases, rust is an immediate red flag. Couple that with the brake system being one of the most important systems in your car, and you’d be forgiven for being a little uneasy about seeing a bit of red on the rotors.

It’s a great habit to do these visual checks first before getting out and driving your car first. That way you can see if you need to conduct some general vehicle maintenance. Though, fret-not as a bit of surface rust isn’t bad. Worry once the rust gets a bit deep or doesn’t go away after a quick drive. 

This boils down to the material of the rotor. Unless you have an exotic car with carbon-ceramic brakes, then your rotors are most likely made out of cast iron, which is prone to rust. Iron oxidizes easily, and rust will form on the surface of the discs if they are exposed to water or moisture.

That being said, most cars on the road whether an SUV or a sedan will experience rusting on the rotors regardless of ride height. Even crossovers experience this phenomenon. From your average Toyota Vios to your more premium Mazda CX-9, since most common cars use cast-iron discs, it’s only a matter of when it rains. 

For most cases, if you leave your car parked outside overnight in the rain, starting your car then coming to a stop once will be enough to wipe the surface rust off your rotors. If your car’s seen some kilometers, then you might see that the top portion or vents of your rotors have rust that is much thicker and darker than the rust on the surface that contacts the pad. Even then, this level of rust is normal, and won’t affect the disc’s performance.

Because oxidation and rust eat away at the metal, it is important to drive your car regularly and engage the brakes in order to wipe off the accumulated oxidation on the surface of your rotor. Surface rust becomes a problem once it gets deeper and starts eating away at the structural integrity of the disc. 

Either fix is not always needed but if, however, you find that your rotor is beyond the normal fix, then you might need to take your car to a machine shop where they will grind away the rusted surface of the disc leaving a nice clean and bare area for your calipers to clamp down and your brake pads to make good contact.

If the damage is too severe, or your machine shop deems your rotor beyond repair, then getting a new set of rotors will solve your issue.