Grating sound

[step_change]

Hi all,
Other day when started up I heard a faint metallic grating sound, rotational related, from the offside rear wheel when I drove off, it sounded like something dragging on floor but there wasn't. It never did it before. Rear brakes were replaced two months ago and have been fine. It went away after a mile of driving and has not come back since... Car drives perfectly, brakes perfectly, no dashboard lights. Also drove perfectly during this grating too.

What do you reckon?

 

[patriot66]

Stone or debris between the disc and back plate ? I had this once on my old 328i...helluva noise for a few minutes then stopped.

 

[step_change]

Stone or debris between the disc and back plate ? I had this once on my old 328i...helluva noise for a few minutes then stopped.

That's what I was thinking, not sure what else it could have been.

 

[Fox889]

Lazy calliper/pad & as soon as it's warmed up will expand?