Likely causes are:
1) back of pad rubbing on caliper or caliper piston.
2) glazing on either the pad or rotor
3) (much less likely) some part of the brake system may be rubbing when braking.
I would suggest disassembling the brakes, and lightly sanding the face of the pad (the part that rubs on the rotor) with some medium grit sandpaper. You don't have to sand hard, all you want to do is break up and glaze on the surface. Then get some "brake quiet", this is usually sold as an spray or in a tube. Spray that on the *back* of the pad (the part that doesn't touch the rotor). DO NOT get any on the rotor or the face of the pad as it will negatively affect braking. Re-assemble the brakes and take it for a test drive.
If the glazing is on the rotor, it will need to be replaced or resurfaced to remove it.
Replace rotor / cut rotor & replace brakes.
Your brakes are probably getting low and they are rubbing against the rotor.
The minimum front brake rotor thickness is three aids of an inch. When the rotor does not have the minimum thickness the auto mechanic replacing the brakes can not use the rotor.
The front brake rotor, on a 2004 Chevrolet Colorado, can be removed by first removing the wheel. Next, remove the brakes. The rotor will slide off
disc brakes in front and rear ( rotor ) Also , the rear rotors have a small drum on the back of them for small emergency brake shoes
Worn bearings, loose rotor, warped brake rotor, sticking brakes.
When the brake pads are worn the rivets will actually touch the brake rotor when the brakes are applied. The brakes should be changed immediately.
Warped rotor is the most likely cause.
Older helicopters had noisy rotor blades, modern ones are very quiet.
If the the brakes replace from a dealer for the front brakes including re-surfacing the rotor disc is.......$420.00
first off are they disk brakes, (like the front one)? or drum brakes?
Periodic front disc brake adjustment is needed to prevent rotor warpage