Its probably the metal wear indicator on your brake pads squealing to let you know that your pads are almost worn out.
When the "Brakes" light on your dash comes on, or if you hear "metal to metal" scraping from them.
check to make sure brakes are not worn out and scraping
Pads--and if you've got disc brakes on the back of the car, which I think you do, you need pads back there too.
Could be the bearings.
Yes; the Volkswagen Jetta tdi had a thick disk brake in the front end and the rear disk brake is larger in diameter than the front brakes but not as reinforced.
Could be lube/oily substance on the pads.
My car has only 122K mi on it. The pads are only about 1/2 worn out.
Could be the dust shield is scraping the rotor causing the noise.
This may be a wheel bearing problem.
Front pads (disc brakes) Rear shoes (drum brakes)
Could be a few things, maybe as simple as a portion of the inner skirt is rubbing on a tire when turning. Could also be a wheel bearing, front axle cv joint (front wheel drive) or even worn down brakes. In any event I would have a mechanic take a look at it before it could get costly and dangerous.
your back brakes are supposed to apply before your front brakes, they do this so your car does not take a nose dive every time you apply the brakes. but if it is very noticeable i would check the adjustment of your rear brakes (if you have a disc/drum setup) or i would check your proportioning valve if they are locking up