If your vehicle is showing brakes grab or lock up with very little pedal pressure, here are the most likely causes and the parts you'll need to fix each one.
Overnight moisture causes a thin layer of flash rust to form on the braking surfaces. This makes the brakes extremely grabby for the first few stops until the rust is scraped off.
If brake fluid, axle grease, or engine oil leaks onto the brake pads or shoes, it changes the friction coefficient and causes the brakes to grab violently instead of stopping smoothly.
If the caliper slide pins lack lubrication or have torn boots, the caliper cannot center itself. This causes the pad to bind and grab the rotor suddenly. Often caused by failing to grease pins during a recent brake job.
An old rubber brake hose can break down internally, acting like a one-way check valve. It allows fluid to push the brakes on easily but traps the pressure, causing them to lock up or drag.
If the master cylinder or brake booster was recently replaced and the pushrod was adjusted too long, it keeps constant pressure on the master cylinder. The brakes will grab instantly and eventually lock up as fluid heats and expands.