Q: I drive a 2000 convertible that is frequently parked for seven to 10 days. It appears the front brakes rust in that time and then stain the driveway. What can I treat them with to prevent driveway stains?
A: What you’re experiencing is casually referred to as lot rot. The metal in brake discs is constantly scraped bare by the pads and subject to extreme heat cycling that causes microscopic fissures in the surface – basically it’s a perfect breeding ground for rust. This effect is accelerated in places with high humidity or heavy rainfall; rotors can even show rust overnight in the right conditions, even though it doesn’t really damage the rotors. I’m assuming you live in a very humid climate, and at night condensation forms on the rotors, then drips off, carrying small amounts of rust with it. There’s not much you can do to prevent the oxidation problem. If you’ve replaced the rotors in the past, the steel in the new parts may not have been up to the original equipment standard. A set of higher-quality brake rotors may reduce the rustiness.
As to the spots on the driveway, believe it or not, a simple acid solution will clean the rust away in a jiffy. Grab lemon juice or vinegar, pour some on the spot, and scrub with a hard-bristle brush, then let it sit for a few minutes. Rinse the stains with a garden hose and the concrete or asphalt surface should be clean as a whistle.