Your Trusted Garage Door Extension Spring Supplier
KOP DOOR delivers complete extension spring solutions designed for wholesalers, distributors, door manufacturers, and contractors. Our springs are produced from high-tensile oil-tempered steel wire (high-carbon steel 72B/82B) with controlled coiling and surface protection, supporting both standard and non-standard garage door applications. Available in multiple wire diameters, lengths, and end styles, they provide stable tension, reduced stretch fatigue, and cycle performance suited to everyday and higher-frequency use.
We focus on steady B2B supply—competitive bulk pricing, flexible packaging, private labeling, and technical support aligned with your inventory needs and project timelines. Both European and American styles have corresponding door panels. For South American market we offer special springs of 65KG, 75KG, 100KG, 125KG and 150KG.
Garage Door Extension Springs
- Model: KST 05
- 7ft door / size:25-42,8ft / size:27-48
- Electrophoretic treatment, light blue color coding
- Customized length available, DASMA color coding available
- Size stencilling and label tying available
- Model: KST 06
- 7ft door / size:25-42,8ft / size:27-48
- Electrophoretic treatment, light blue color coding
- Customized length available, DASMA color coding available
- Size stencilling and label tying available
- Model: KST 07
- 7ft door / size:25-42,8ft / size:27-48
- Electrophoretic treatment, light blue color coding
- Customized length available, DASMA color coding available
- Size stencilling and label tying available
- Model: KST 08
- 7ft door / size:25-42,8ft / size:27-48
- Electrophoretic treatment, light blue color coding
- Customized length available, DASMA color coding available
- Size stencilling and label tying available
- Model: KST 09
- 7ft door / size:25-42,8ft / size:27-48
- Electrophoretic treatment, light blue color coding
- Customized length available, DASMA color coding available
- Size stencilling and label tying available
- Model: KST 10
- 7ft door / size:25-42,8ft / size:27-48
- Electrophoretic treatment, light blue color coding
- Customized length available, DASMA color coding available
- Size stencilling and label tying available
- Model: KST 11
- 7ft door / size:25-42,8ft / size:27-48
- Electrophoretic treatment, light blue color coding
- Customized length available, DASMA color coding available
- Size stencilling and label tying available
- Model: KST 12
- Length over coils: 28 in.
- Wire gauge: 0.244 in. (no. 3 wire)
- Initial tension: 165 lbs. – 185 lbs.
Stable Tension & Balanced Operation
Our garage door extension springs provide consistent pulling force along the door travel path, helping reduce stress on tracks, cables, and operators. Proper spring selection matched to door weight supports smoother, more controlled movement and safer everyday use.
High-Tensile Materials & Fatigue Resistance
Manufactured from oil-tempered high-tensile steel with precise coiling and heat treatment, these garage door extension springs resist stretch set and fatigue under repeated cycles. They are suitable for residential doors as well as higher-cycle commercial environments when correctly specified and installed.
Flexibility & Reliable Supply
KOP DOOR offers extension springs with custom wire gauges, free lengths, end styles, surface treatments, private labeling, and packaging (2 pieces per individually wrapped package，wooden cases ，nude packing for container shipment). We support distributors and manufacturers with stable lead times and volume pricing.
Garage door extension springs are specially designed for the repeated up-and-down cycle of garage doors. They feature calibrated initial tension, reinforced end hooks and high fatigue resistance matched to door panel weight. Standard industrial extension springs are not tuned for door counterbalance.
Open-loop ends allow easier attachment with hooks or clips and are common on many residential doors. Closed-loop ends form a continuous loop for more secure connection and are often preferred for heavier doors or applications requiring higher safety margins. Both styles can be supplied to match your hardware system.
We use high-tensile oil-tempered steel wire (commonly 72B / 82B grade or equivalent). Surface treatments such as galvanizing, e-coating, or powder coating are applied to improve corrosion resistance for long-term outdoor exposure.
Cycle life depends on door weight, usage frequency, and correct installation. Our standard extension springs typically support 10,000–25,000+ cycles under normal conditions. Heavy-duty options for higher-frequency commercial use are available upon request.
Excessive tension: The door opens too fast and slams hard when closing, risking damage to panels, hinges and garage door operator.
Insufficient tension: The door cannot lift properly, overloads the opener and may drop by itself, which creates safety risks. Spring tension must precisely match the door panel weight.
Yes. We keep popular standard sizes in stock for quick shipment and accept custom wire diameters, free lengths, end styles, stretch rates, surface finishes, and private-label packaging for bulk or OEM programs. Share your technical drawings, volume forecasts, and packaging preferences for a tailored quotation.