Never overlook needed brake repairs to your vehicle's brakes, as even a small problem can quickly escalate so that those brakes suddenly outright fail when on the road. The good news is that your car's brakes often send you signals that they're in need of repair long before they actually fail, so you can have them fixed or replaced as necessary, keeping you safe on the road. Note a few things that might be wrong with the brakes when they do begin to act up, so you can know what to expect by way of repairs and also know why these problems need to be addressed quickly.
One of the most common causes of grinding sounds and a grinding feeling from the vehicle's wheels is worn down brake pads; once these get thin, you're squeezing metal against metal and this makes the brakes grind. However, the rotors can also be worn and not thick enough to push back against the pads when they squeeze closed, so you hear this grinding sound. Dirt, dust, and other debris getting caught under the pads can also cause this sound; the pads usually need to be changed when this happens.
If your brakes tend to work fine one minute but then feel very loose, meaning that you don't have full stopping power, this often means that the brakes are lacking proper brake fluid. This fluid builds pressure in the braking system so the pads can squeeze shut; if it's not being delivered at a consistent rate, the braking may be sporadic. The brake lines may have a leak, or they may have air in them that interferes with proper flow of the brake fluid. The lines can be bled if there is air, or they will need to be replaced if they're damaged and leaking.
When you release the brake pedal, the brakes should immediately let up and there should be no resistance. If the brakes continue to work after you release the brake pedal, this can be worn callipers, which are the clips that squeeze the pads against the rotors. This can also be a slipped or damaged brake pad, which will still grip the wheel even after the callipers have released it. A bent axle, bent tyre rim, misaligned tyre, or oversized tyre can also cause the pad to keep squeezing even after you release the pedal. If the brake pads are in good condition, have your mechanic examine the tyre and attached pieces for any such damage.