There has been alot of discussion out there with Centurion fans that the 1989 Centurions had different gemetry frame than the prevoius years. Well i cannot speak for 1988 but i can tell you that 1987 and 1989 Geometry are different in the frames. There seems to be a 2 degree decrease in headtube angle. which would make it a quicker steer . Also Chainstay to Seatstay angle is decreased by 1 degree for 1989 from 1987.
My Basis for comparison are matching size frames both 60cm one is a 1987 Ironman Expert (Magenta/Yellow) and a 1989 Ironman Expert (Black)