2011 fiesta zetec - weird noise

[fiestaz]

Hi all,

went up the coast last weekend. all was well (averaged 5.7l/100kms ) came home parked up. 2 nights later i drove just up the road, and in this carpark at my local shops i could hear this sort of intermittent whooshing/sort of a grinding noise (really hard to describe it sorry) between 15-30km/h it is most noticeable and the faster i drive the faster it gets. my first thoughts were brakes were grabbing or pads rubbing on the disc.

took it too ford. on the way there i noticed that in a straight line it gets quieter as the car warms up, however when going around a tight round a bout or cul de sac you can really hear it still, warm or cold. fords technician heard it and said its not the brakes its the tires, something about an air gap between the alloy and tyre. this didnt really make sense to me as it really doesnt sound like a tyre noise. plus tyres and rims are original and nothing has changed with them apart from the odd tyre rotation and alignment. he pumped the front tyres up (not that they were at the wrong pressure but as a possible problem).

anyway took it home, its still doing it. no change. im going to take it back again next week, and tell them to check the brakes.

was just wondering if anyone has had anything similar or any ideas? we put a temp gun on the brakes after a test drive at home and the drivers side brake disc was 15 degrees hotter than the other side. but with all the Electronic brake force distrubution tech, perhaps this is normal?

any ideas or thoughts appreciated. cheers.