Don't know if a 5% discrepancy (10mm roughly in diameter) in tyre profiles would cause that but who knows. Could it be a sensor playing up causing it to believe that your loosing traction (I'm assuming that TC stands for traction control). It sounds strange that it's happening at 60 though and not at any other time. Does it go off under/above 60? Can't see the correlation between speed and engine misfire though.