The relaxation behavior of substituted bisphenol-h polycarbonates is investigated in the glassy state by mechanical spectroscopy. Conventional bisphenol-A polycarbonate (BA-PC) is compared with polycarbonates based on 1,1’-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (TMC-PC) and 1,1’spiro[bis(3,3-dimethyl-6-hydroxyindane)] (SRI-PC) and random copolymers of the latter with bisphenol-A. In SBI-PC the phenyl flip is not just hindered but completely locked due to the chemical bridge via the spiro linkage. Despite the impossibility of phenyl motion, the gamma-relaxation is observed for SBI-PC at roughly the same temperature as for the other two polycarbonates. This is real proof that the phenyl motion is not required for the typical gamma-relaxation of polycarbonate at low temperature. Consequently, the polymer chain can get its mobility only from the flexibility of the carbonate linkage. It was also found that the width of the gamma-relaxation peak in the SBI copolycarbonates decreases systematically with increasing spiro content. This means that in the rather broad peak in BA-PC there is a contribution of a second damping mechanism at the higher temperature side which is affected by the spiro linkage. That damping contribution is therefore ascribed to the phenyl motion. This also explains why the gamma-relaxation of polycarbonates with ortho-substituted phenyls occurs at much higher temperatures. There the carbonate motion couples to the phenyl motion due to sterical hindrance, which is not the case in SRI-PC.