RR
Reliable Residential
Tech Hub
Spring Specs
Enter the wire size, ID, and length of the spring(s) currently installed.
Advanced Options drum, radius, lift type
Enter spring specs above and tap Look Up Spring to see what it produces and get replacement options.
Door Details
Enter the door weight and height to find the best match.
Advanced Options radius, lift type
Track radius is captured for the work order. Cable take-up is not affected by radius alone — only by high-lift extension.
Enter the door weight above and tap Find Best Spring Match to get recommendations from your truck inventory.
← Swipe table to see all columns →
| Wire Size | ID | Length | Coils (Total) | IPPT | Turns | Lift/Spring (lbs) | Pair Lift (lbs) | Max Turns (10K) | Cycle Life |
|---|
Estimate by Door Type
Common Door Weights
| Door Size | Non-Insulated | Insulated | Wood |
|---|---|---|---|
| 8 x 7 | 75-90 lbs | 100-120 lbs | 150-200 lbs |
| 9 x 7 | 85-100 lbs | 110-135 lbs | 175-225 lbs |
| 10 x 7 | 95-115 lbs | 125-150 lbs | 200-260 lbs |
| 12 x 7 | 110-130 lbs | 145-175 lbs | 235-300 lbs |
| 16 x 7 | 145-175 lbs | 190-230 lbs | 300-400 lbs |
| 8 x 8 | 85-100 lbs | 115-140 lbs | 175-225 lbs |
| 9 x 8 | 95-115 lbs | 130-155 lbs | 200-260 lbs |
| 16 x 8 | 165-200 lbs | 220-265 lbs | 350-450 lbs |
| 18 x 8 | 185-225 lbs | 250-300 lbs | 400-500 lbs |
Wire Size Chart (10/20 Coil Measurements)
| 10-Coil | 20-Coil | Wire Size |
|---|---|---|
| 2 1/16" | 4 1/8" | .2070 |
| 2 3/16" | 4 3/8" | .2187 (.218) |
| 2 1/4" | 4 1/2" | .2253 (.225) |
| 2 3/8" | 4 11/16" | .2343 (.234) |
| 2 7/16" | 4 7/8" | .2437 (.243) |
| 2 1/2" | 5" | .2500 (.250) |
| 2 5/8" | 5 1/4" | .2625 (.262) |
| 2 3/4" | 5 1/2" | .2730 (.273) |
| 2 13/16" | 5 5/8" | .2830 (.283) |
| 2 15/16" | 5 7/8" | .2950 (.295) |
| 3 1/16" | 6 1/8" | .3065 (.306) |
| 3 1/8" | 6 1/4" | .3125 (.312) |
| 3 3/16" | 6 3/8" | .3195 (.319) |
| 3 5/16" | 6 5/8" | .3310 (.331) |
| 3 7/16" | 6 7/8" | .3437 (.343) |
| 3 5/8" | 7 1/4" | .3625 (.362) |
| 3 3/4" | 7 1/2" | .3750 (.375) |
Turns to Wind (Standard 4" Drums)
| Door Height | Turns | Spring Growth (coils) |
|---|---|---|
| 7' 0" (84") | 7.2 | ~7 coils |
| 8' 0" (96") | 8.1 | ~8 coils |
| 9' 0" (108") | 9.1 | ~9 coils |
| 10' 0" (120") | 10.0 | ~10 coils |
| 12' 0" (144") | 12.0 | ~12 coils |
Formula: Turns = (Door Height in inches / Drum Circumference) + 0.5 pre-load
4" Drum Circumference = 12.566"
4" Drum Circumference = 12.566"
Key Formulas
IPPT (Spring Rate):
IPPT = (π × E × d4) / (32 × D × N)
E = 30,000,000 psi | d = wire dia | D = ID + d (mean dia) | N = active coils (total - 5 dead)
Torque per Spring:
Torque = IPPT × Turns
Lift per Spring:
Lift = Torque / Drum Radius
4" drum = 2" radius
Balance Check:
Total Lift = Lift per Spring × # Springs ≈ Door Weight
D × N Trade Rule:
Mean Dia × Active Coils = constant for equal IPPT at same wire size
e.g. 2" ID × 30" long = 1.75" ID × shorter/fatter spring
Inside Diameters by Manufacturer
| ID | Used By |
|---|---|
| 1 3/4" | Most manufacturers (CHI, Clopay, Amarr, Wayne Dalton, etc.) |
| 2" | Most manufacturers (CHI, Clopay, Amarr, Wayne Dalton, etc.) |
| 2 1/4" | Raynor, Rowe Way |
| 2 7/16" | Overhead Door only |
| 2 5/8" | Most manufacturers (commercial) |
| 1 13/16" | Older Raynor, BarCol |
Cycle Life vs. Stress
| Cycle Life | Max Wahl-Corrected Stress |
|---|---|
| 10,000 cycles | 242 Kpsi (standard) |
| 25,000 cycles | 200 Kpsi |
| 50,000 cycles | 175 Kpsi |
| 100,000 cycles | 150 Kpsi |
Stress: S = 32 × Torque / (π × d3)
Wahl Factor: Kw = (4C-1)/(4C-4) + 0.615/C where C = D/d
Corrected Stress: S × Kw ≤ limit above
Wahl Factor: Kw = (4C-1)/(4C-4) + 0.615/C where C = D/d
Corrected Stress: S × Kw ≤ limit above
Field Tips
- Always measure 20 coils for wire size. Calipers alone are unreliable due to corrosion, paint, and wire curvature.
- Spring grows 1 coil per turn when wound. On a wound spring, deduct that many coils from the measured length to get the relaxed length.
- Chalk line trick: Run chalk down the relaxed spring before winding. Each time the line comes back around = 1 turn. Lets you count turns without losing focus.
- ID is on the cone. Look for stamped markings like "175", "200", "134", or "263" on winding or stationary cones.
- ~30% of doors have mismatched springs. Always measure both springs individually -- manufacturers and previous service techs mix sizes to save on inventory.
- Trading D for L: If you don't have the exact spring, a different ID with adjusted length can produce the same IPPT. Mean dia times active coils stays constant for equal rate at the same wire size.
- Heavier wire = longer life. Going up one wire size and adjusting length can dramatically increase cycle life (stress drops with the inverse cube of wire size).
- Lock the door down before winding. Disconnect opener, clamp the door shut. An overspring situation without the door locked can launch it open unexpectedly.