The invention is directed to a center deck assembly (100) for a tire building drum. The tire building drum is rotatably mounted on a central drive shaft and includes a center section (110) . The center deck assembly is disposed in the center section of the drum and includes a hub (112) that seats on and is secured to the central drive shaft. At least one piston (124, 126) extends circumferentially in the tire building drum about the hub and a plurality of segment bars (186) are disposed about the circumference of the center deck assembly. The at least one piston (124, 126) is operably connected to the segment bars by a plurality of linkages (154) , in which each of the linkages (154) includes a scissor-lever mechanism.