check brakes and disc on all four wheels they may be worn.
The disc pads are worn out. The grinding is metal to metal contact of the pad backing plate and the rotor. Have the pads replaced and the rotors turned or replaced whichever is applicable. This is a very dangerous situation and should be repaired ASAP.
Incorrect pad / disc combination. There are specific blends of pads that are designed for disc brakes. Some need more metallic components, and some have less. Try the recommended OEM pads for the vehicle.
The brake pads could be worn out
Shimano BO1S Resin pads
Disc brake pads and drum brake shoes
Lots of practice, wear a helmet and pads.
New brakes do not grind. If you replaced the brake pads and resurfaced the rotors you may hear a bit of a sound but it is normal until the pads and rotors wear during normal driving.
Disc brake pads are typically made of materials like ceramic, semi-metallic, or organic compounds.
The purpose of breaking in new disc pads is to ensure proper contact and friction between the pads and the rotor, allowing for optimal braking performance and longevity of the braking system.
The scraping noise from your bike's disc brakes could be caused by misalignment of the brake pads, contamination on the rotor or pads, or worn brake pads.
what kind of wrench to remove brake pads
Disc brake pads push in. they pinch the rotor