no problem, then just started up my 03 sl500 today and the noise just started from the front passenger tire area. It is a very loud squeak and sounds like metal on metal like something is really dry that is rubbing. applying the brakes had no effect. just driving in a straight line it makes this horrible noise. it brakes fine. I tried going in reverse and pumped the brakes and that seemed to stop the noise for a couple of minutes and then it came back. does the same fast or slow and did seem to be just a tad worse when turning. do not know if I should drive it to garage because it really sounds bad. I sure would appreciate any help I can get

 

Given your description, I would look at a wheel bearing ....perhaps a collapsed bearing race cage.Quickly check by firmly grasping the top of the wheel and attempt to rock from side to side. If bearings are loose or damaged, there will be some play.

 

I had something like this on my Audi A6 about 4 years ago and again last
saturday on my BMW 540. Turns out a little rock or pebble gets caught between the splash shield and the rotor. That may be why it stops when you reverse. I took the wheel off and sure enough, there was a pebble with a small polished area from rubbing. It sounded like hell!

I hope it is something as simple as this for you!

Cheers!