Rust on brake rotor — Replace or clean?
What causes rust on brake rotors?
All brake rotors rust. However, some rust faster than others. How quickly it rusts and how badly it rusts depends on the quality of the brake rotor and the cast iron used and in some cases, how long it sits unused.
Letting your vehicle sit unused will cause the rotor face, hat and cooling vanes to rust. When you finally drive the vehicle, the brake pads will wipe the surface rust off the friction ring area and after a few braking cycles, you’ll have full braking power.
However, if you let the vehicle sit for too long, the rust can pit the surface of the friction ring and that pitting can’t be wiped off though brake applications.
Surface brake rotor rust versus serve pitting
Here are some examples of severe brake rotor rust that can’t be removed by normal braking. These rotors must be replaced; they can’t be saved by machining.
How to prevent rusted brake rotors
Drive the vehicle to remove AND prevent brake rotor rust
The best way to prevent rust on your brake rotors is to drive the vehicle. Letting it sit unused in humid conditions will always cause them to rust. Driving the vehicle heats up the rotor to evaporate off moisture and the brake pads wipe off surface rust.
Purchase coated brake rotors
Some high quality brake rotors come with an anti-corrosion coating. That coating wears off the friction ring surface of the rotor as you brake. But the rest of the coating slows down corrosion on the hat and inside the cooling vanes.
The anti-corrosive coating inside the cooling vanes helps prolong the life of the brake pads by keeping the friction ring surface cooler.
Some economy rotor manufacturers are now offering coated rotors, but applying an anti-corrosive coating to a low quality rotor is like putting lipstick on a pig. If the base metal is of poor quality, the friction ring will begin to rust as soon as the coating wears off.
Remove brake rotor rust
The best way to remove rust from the friction ring is to simply drive the vehicle and brake. The brake pads will remove surface rust.
To remove rust from both the inside hat area (the portion that mates to the wheel hub) and the outer hat, use an abrasive pad and drill. The use the abrasive pad to remove rust from the wheel hub.
You can use chemicals to remove rust from the hat and cooling vanes, but unless you apply a high temperature rust prevention coating, the rust will return.
Posted on by Rick Muscoplat
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