review dismantle of caliper. if it was difficult to open them, then pistons may need to cleaned and lubed. if old pads wear was lopsided, than may need to replace caliper. also review fluid colour. may need to bleed and renew. worst case is collapsed break line. doesn't happen often but it does.
At any point in the process of changing the front pads , did you bleed the brakes and possibly add the wrong type of fluid to the M/C? After 10-12 miles and the car comes 'to a stop' are the front rims REALLY hot?