The reason for this sound is a low-quality friction mixture. As a result of its use, the brake discs and hub are greatly heated. The hub may also be heated because of the bearing of the bearings, the lack of lubrication in it, the frequent braking of the car (for example, traffic in traffic). A little whistle doesn't talk about a malfunction. You can't lubricate the lubricants or use diesel fuel. With a strong whistle, you'd better show the car to the specialists.
