When it rains the left front brake makes a scrubbing sound and has a small vibration. After using the brakes once or twice it goes away. It sort of feels the the rotor is warped. But, it only happens in the rain and then goes away. I had the dealer look at it several times since I bought this car in 2008 and they claim they can’t find anything wrong with it.
Rust builds up on brake rotors and drums really fast, and much faster in wet weather. You are likely just hearing the surface being scrubbed off the first time or two that you brake. If you’re really that worried, take it somewhere else for an independent second opinion - a good local shop rather than a chain operation.
It is common for rotors to rust overnight in moist conditions. My vehicle would sound like metal to metal destruction until I used the brakes one or twice. Don’t worry, be happy, it’s normal.
I don’t how to explain it but this seems different. I had a Neon and the rear brakes made the scrape the rust sound every morning. This doesn’t happen until the brakes get wet. And the car seems to pull to the left when it happens. After it starts, it does it 1, 2 or 3 times then everything is fine. I live on a gravel and dirt road and I wonder if that has something to do with it.
You didn’t mention the slight pulling to the left. Now I’m led to wonder about a problem in your ABS system - the noise, maybe some pulsing in the pedal? (You mentioned vibration/warped rotor).
Come to think of it - are you sure the pulling isn’t your imagination? Because now it does just sound like normal ABS operation - Rain + noise + vibration? = ABS kicking in when you’re trying to stop too hard.
It’s not the real high end Focus, so no ABS. The pulling might be my imagination. I’ve been wondering if instead of rust it’s scraping off, maybe it’s dried mud from my driveway.