If your 60 to 100 kg sectional door lifts with one hand, it is thanks to a precise balancing system mounted above the lintel: the torsion axle. Knowing it helps you spot wear before breakage.
The key components
- The torsion shaft: a steel tube spanning the door's width, transmitting spring energy to the drums
- The torsion springs: coiled around the shaft, they load as the door closes and return the energy on opening; their life is counted in cycles (10,000 to 25,000 depending on quality)
- The drums: grooved pulleys at the shaft ends where the cables wind
- The lifting cables: they link the drums to the bottom of the panels and actually carry the door
- The bearings: they guide the shaft's rotation
How the system balances
Spring torque is calculated to offset the door's weight almost exactly at any height. A well-adjusted door stays put at mid-travel, neither rising nor falling: that is the reference balance test (done with the motor released).
The wear signs to watch
- A door heavy at mid-travel or a straining motor: springs losing torque
- A violent bang in the garage: spring rupture — stop using the door
- A slack, frayed cable or one off its drum: immediate intervention
- A door rising crooked: unequal tension between the two sides
Warning: springs and cables under tension cause serious DIY accidents every year. Replacing them demands winding bars and method. Our technicians service and replace sectional-door axles, springs and cables throughout Île-de-France.