Did you check if the rear rotors were dragging? Park brake might need adjusting.
Pull the rear wheels off and you'll see a rubber bung on the rotor hat. Remove that, line it up with the little gear wheel at the bottom (you will need a torch), and use that to adjust the resting position of the park brake shoes. You want to wind it up all the way with the footbrake OFF so that the rotor can't move, and then back it off a bit until it can spin freely.