Hello, I am driving a 2011 mk 2.5 focus (140k km) and I started hearing a high pitched noise coming from the back of the car (driver side, rear wheel). The noise sounds similar to a bike brake used on rainy weather, but it is not continuous and seems to be related with how fast the wheel is spinning (from what I can tell I hear it once for every wheel rotation). The noise can only be heard when taking corners and only under 40 km/h. When the car is fully loaded it can be heard even when slightly turning the steering wheel or even when going over bumps while driving straight. When I am driving without passengers I have to take the corner a little bit faster in order to hear it. It seems to me like it is related to the wheel load (the heavier the load on that wheel, the louder the noise). The noise completely disappears after 40-50 km/h regardless of how fast I am taking a corner. I have just done a 4 wheel alignment, but that didn't fix the problem. I changed all 4 rotors and brake pads 1 year ago (20k km ago). Do you have any ideea where that noise might come from? Thank you! 

If it's more of a chirp I'd take a gander at the bushes, most common thing I've come across on the mk2s and the FLs has been the lower arm bushes on the front which does exactly this, as they end up on their way out they chirp over bumps, especially when dry, as if you've just tonked a bird and it let's out a brief squeak- very very specific and recognizable if you ever hear it up front, but not to say it doesn't sound the same at the back!

If anyone has a similar problem, almost 2 years later I've found the cause of this. The rhythmic sound comes from the brake pads touching the discs. If I brake hard a few times (or run a few seconds with the handbrake on) enough for the pads and discs to be hot, the sound disappears or greatly diminishes. I guess the fact that the brake disc touches the pads when turning is another issue (maybe some play in the bearing or the fact that my rear rims are a little damaged). So if anyone has this issue, make sure to also check the brake pads/discs.