GM cars, SUVs may have weak rear brakes medium
The pistons inside the rear brake calipers, the parts that squeeze the brake pads against the wheels, were not coated properly. That can let gas pockets form in the brake system at the rear wheels. Gas squashes when you press the pedal instead of pushing firmly on the pads, so the rear brakes do less of the work and the vehicle can take longer to stop than you expect. The dealer bleeds the brake system to clear the gas out.