Tools
Torsion spring calculator
Size a balanced torsion spring set from the door weight and height, or measure an existing spring to find its exact replacement — wire size, inside diameter, length, turns and cycle life.
Weigh the door on a bathroom scale with the springs unwound.
Turns
7.43
Full turns to wind
Torque needed
280 in-lb
Door weight × drum radius
Rate per spring
18.8 IPPT
Each of two springs
Recommended spring (×2)
0.2500" wire · 2.25" ID · 54.75" long
Rate
18.8 IPPT (-0.0%)
Wire stress at full wind
98,600 psi
Estimated life
100,000+ cycles
Right-wound (RHW) — Red cone
Left side of the center bracket
Left-wound (LHW) — Black cone
Right side of the center bracket
| Wire | ID | Length | IPPT | Cycle life | |
|---|---|---|---|---|---|
| 0.2500" | 2.25" | 54.75" | 18.8 | 100,000+ cycles | Find |
| 0.2625" | 3.75" | 43.5" | 18.8 | 100,000+ cycles | Find |
| 0.2500" | 3.75" | 34.25" | 18.8 | 100,000+ cycles | Find |
| 0.2730" | 3.75" | 52.75" | 18.9 | 100,000+ cycles | Find |
| 0.2500" | 2.625" | 47.5" | 18.9 | 100,000+ cycles | Find |
| 0.2437" | 2.625" | 42" | 18.8 | ~50,000 cycles | Find |
| 0.2437" | 2.25" | 48.25" | 18.9 | ~50,000 cycles | Find |
| 0.2437" | 2" | 53.75" | 18.8 | ~50,000 cycles | Find |
| 0.2343" | 2.625" | 34.5" | 18.9 | ~50,000 cycles | Find |
| 0.2343" | 2" | 44.25" | 18.8 | ~25,000 cycles | Find |
| 0.2343" | 2.25" | 39.75" | 18.9 | ~25,000 cycles | Find |
| 0.2343" | 1.75" | 49.75" | 18.9 | ~25,000 cycles | Find |
How the math works
Rate (IPPT) = E × wire⁵ ÷ (10.8 × mean diameter × coiled length), with E = 28,500,000 psi for oil-tempered wire and mean diameter = ID + wire. Torque needed = door weight × drum radius, delivered over the lift turns (door height ÷ drum circumference) plus a 3/4 preload turn.
Cycle life
A cycle is one open and one close. Lower wire stress means longer life — going up in ID and length with a bigger wire buys 25k–100k cycles on the same door.
Safety
Wound torsion springs store enough energy to kill. Use proper winding bars, never screwdrivers, and let a trained tech do the install if you are unsure.