Why do my brakes squeak? Do I have an incorrect distance between brake pads and rims? My brakes were working normally until I adjust them today. I thought the brake pads were too close to the rims so I increase the distance a bit. Now every time I brake, they make horrible squeaking sound. However, when I test them in slow motion, they won't make that noise. My guess is only when the bike is moving fast, the brake pad cannot hold the wheel strong enough; consequently, the wheel slides on the pads causing the squeaking noise. Please correct me on that if I'm wrong.

Now, I wonder if there's any golden rule on the optimal distance between brake pads and rims?
I'm not aware of any established best practices other than "as close as possible, without any rubbing through a full revolution of the wheel".