Torsion spring tensioning tool

Torsion spring tensioning tool (100) for tensioning a torsion spring of a counterbalancing mechanism of an overhead door, wherein the torsion spring tensioning tool (100) comprises a housing (80), a gear wheel arrangement (20) adapted to be mounted on a shaft of the counterbalancing mechanism, said gear wheel arrangement (20) comprising a gear wheel (21) rotatably arranged in the housing (80), the torsion spring tensioning tool (100) further comprising a gear mechanism (54) coupled to the gear wheel (21) for rotating said gear wheel (21), wherein the gear wheel arrangement (20) comprises a fixating arrangement (32, 320) fix to the gear wheel (21) and adapted to engage the shaft of the counterbalancing mechanism and transmit a rotational movement from the gear wheel (21) to the torsion spring, the torsion spring tensioning tool (100) further comprising a support gearing (50) in engagement with the gear wheel (21)) such that the gear wheel (21) is arranged between the support gearing (50) and the gearing mechanism (54).