Why are my Ford Fiesta's brakes whirring?

I bought a 58-plate Ford Fiesta Zetec S (new shape) in May 2010. It has been great, however I've noticed that when I'm braking there is an odd whirring-type sound when speed gets below 15mph or so. It doesn't happen when driving normally or accelerating - only braking. It almost sounds like something catching, but I've no idea what it is? Does anyone have any ideas?

Asked on 14 July 2010 by fiestaownerkford

Answered by Honest John
If it doesn't go very far it could be surface rust being scraped off the discs by the pads.
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