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rob's garage

Hi Rob,

I've noticed that the brake discs (I think that's what they're called) on my new Infiniti G37 are covered in rust. I checked all around the car and all four rotors were rusty.

My kids are grown and I just treated myself to my newest baby and I'm not liking what I see. Do I need to be concerned? What's going to happen the first time I apply the brakes each morning on my way to work?

Thanks for any light you can shed on this matter, Jonathan.

Not to worry Jonathan, rusty rotors are perfectly normal - most drivers weren't able to see this rust on their cars until fairly recently, but larger wheels, combined with fewer spokes, make brake parts more visible.

Being able to monitor how the friction pads and rotors are wearing is a good thing. With the exception of fully ceramic rotors, most production rotors are made of cast iron.

The nature of disc brake operation is such that the friction pads constantly wear away at the surface of each rotor. Each time you park your car, the freshly minted surface of each rotor is exposed to the elements. As you have discovered, the fresh unprotected cast iron will begin rusting almost immediately.

The layer that forms is what's known as surface rust. This is the electrolytic process that takes place on the boundary layer or outermost surface of the cast iron. Rust can occur in less than 12 hours. The first brake application will shave off the rust.

Verify that you have rusty rotors. Drive, then apply the brakes normally. Your rotors should be shiny. If this is the case, you've got nothing to be concerned about.

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