For a few weeks now, whenever I drive in the rain my brakes squeal in an annoying way. When they dry out it goes away and I don't have any braking issues. I tried cleaning the discs with WD-40 but the problem comes back. What could it be?
When it's humid, brakes whistle because a layer of oxide forms on the discs and pads, and when everything's wet the friction creates that annoying noise that goes away once they dry out. WD-40 won't fix it because it's just a temporary lubricant - what you need is to get your brakes working properly with a few solid braking applications while it's raining to "clean" the discs naturally, or if the whistling is really unbearable try replacing the pads because they might have oxidized too much.
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