Whenever the humidity is high or it has rained and my car has sat for about 2-3 hours, the first few feet in reverse produces a high pitched metallic rubbing noise. Put my foot on the brake and the noise stops. Put the car in drive and move forward, noise stops. This only happens in reverse and after the initial braking it goes away.

I think the pads on the RR caliper are absorbing moisture and dragging on the rotor. One stop seems to adjust the clearance.

Anyone else having this occur?

 

More likely the rain has just gotten between the pad and the rotor and is acting like a lubricant. Have you ever noticed how after you wash your car the brakes tend to squeal sometimes? After you have applied the brakes a couple of times it usually quits. I'm pretty sure it's the same deal.

 

Besides rainy days, everytime my car is washed, I have the same noise.

 

This is normal

 

this is normal????? i've only heard it once after a car wash during the break in period and never again (8,000 miles so far)

 

I've never had this happen on my TL but when I first had my 01' A6 I had the same problem. I took it in to the dealer but they were unable to replicate the sound or find anything wrong. It eventually went away after a couple of months. No problems seemed to arise from this noise.

 

the rotors rust, they are just steel after all, and the brake pads scratch the light rust powder off. When you say after rain, and after washing it, it just verifies it. look at them after they sit, they turn nicely orange. nothing you can do about it, they are just steel.

 

I inspected the rotor last night. No rust. Sprayed it down with Brakleen.
This morning as I was backing out of the garage it made the metallic scraping noise again!