A seat belt retractor for a safety belt including a seat belt spindle for winding up and unwinding the safety belt and a tensioning drive. The seat belt spindle includes a gas generator, a drive wheel and a supply pipe which connects the gas generator and the drive wheel. A plurality of thrust members are present in the supply pipe which, after triggering the gas generator, are accelerated and indirectly or directly drive the drive wheel for winding up the safety belt. An inertia coupling is arranged between the drive wheel and the seat belt spindle. The inertia coupling comprises coupling elements which, during an acceleration of the drive wheel, pivot outward and are directly or indirectly coupled to the seat belt spindle.