
Low rumbling noises may be wheel bearings - I have never had this problem, but the dealer mentioned it when I took my car in for service with a strange noise! Brake pads tend to whine as they wear down past their usable thickness. I have had both my cars need new brake pads recently, and both made high pitched whines (usually when driving along and NOT braking).
Another cause of rumbling is a seized brake disc. Ie. the pad (usually a very worn down one) seizes to the brake disc. I have had this happen a number of times (car is a Subaru Impreza Turbo, and the brake discs seem prone to getting dirt etc in them and seizing - roughly once a year so far!) It feels as if you are driving on a road that is bumpier than it should be (and noisier), and the brake disc will get very hot indeed. If you are unluckly you will need new discs, otherwise it may be cured by just new pads. Discs are much more expensive to replace than pads (hundreds of pounds - and they must be replaced in pairs, as must the pads - both fronts or both rear or all of them!)
If anyone lives in or near Hampshire I recommend Micheldever Tyre & Auto Services for brake pads, discs, tyres, suspension problems etc. Much cheaper than most dealers, although my dealer has learned that unless he drops his tyre prices we will drive to Micheldever!
Claire