Bike (Bicycle) Brakes Won't Stop Squealing?

There are 3 common reasons brakes squeal.
1. rim/pads are dirty or pads have forgien material embedded in them
2. pads are old or too hard
3. pads not toed in

You said you cleaned the rims and pads. Did you use alchohol or similar cleaning agent?

Your pads could be poor quality, glazed or too old and dried out making them hard. You can try sanding the pads which would remove the harder, glazed material.

Toe in is needed to keep brakes quiet. The leading edge (front edge) of the pads should hit the rim slightly before the back part. Many pads can be adjusted for this on MTBs etc.

However, many road bikes with dual pivot brakes don't have this adjustment. In this case you could simply bend the brake caliper to adjust (on cheap brakes only) better road brakes are thick and you wouldn't want to bend expensive parts. On good road brakes you can sand the pads to achieve toe in or buy pad holders that allow toe in adjustments.

The pads need to toed in; they need to mounted so that they slant inwards towards the front of the bike. This is because the motion of the wheel pushes the pad and if they are straight on the the wheel a smaller area of pad is applied, hence higher pressure and squeak.

The pads need to toed in; they need to mounted so that they slant inwards towards the front of the bike. This is because the motion of the wheel pushes the pad and if they are straight on the the wheel a smaller area of pad is applied, hence higher pressure and squeak.