Three people were slightly injured this afternoon when the tire of a fire department truck blew out, shattering the glass of a store at 160 Delancey St. It happened at around 1:45 p.m., as Ladder 18 from the Pitt Street station pulled up alongside the north side of Delancey Street for a routine building inspection. A piece of metal on the sidewalk apparently punctured the tire, causing the accident. Flying debris hit three pedestrians. None of them required hospitalization.