Extension springs do the heavy lifting on one side of your garage door

An extension spring is a long, coiled metal spring that runs along the top inside edge of your garage door frame, usually one on each side. When the door closes, these springs stretch and store energy. When you open the door, that stored energy helps lift the weight of the door itself—without them, you would be pulling up several hundred pounds by hand.

Extension springs eventually wear out and snap. When one breaks, you will hear a loud bang and the door will feel much heavier to open, or it may not open smoothly at all. The broken spring will be visibly separated or hanging loose inside the frame. Replacing a broken extension spring is a task you can do yourself if you are comfortable working with tools and understand the safety steps involved.

The process takes about 30 to 45 minutes per spring once you have the right parts and tools on hand. The hardest part is not the replacement itself—it is safely managing the tension in the spring system while you work.

Key Takeaways

  • Extension springs are under high tension and can cause serious injury if released suddenly, so you must find the door and release tension before touching any spring.
  • You need the exact spring size and tension rating for your door, which you can find on the spring itself or by measuring the coil diameter, wire thickness, and total length.
  • A C-clamp on the door track prevents the door from rising unexpectedly while you work, and a winding bar lets you safely adjust spring tension without using your hands.
  • The replacement process involves removing the old spring, installing the new one on the same bracket, and then winding it to the correct tension using a winding bar.
  • If both springs are old, replace them both at the same time so they wear evenly and the door stays balanced.

Gather the right tools and safety gear before you start

You will need a winding bar (a long metal rod, usually 1/4 inch diameter, that fits into the holes on the spring's winding cone). Do not try to wind a spring by hand—the bar is essential for safety. You also need a C-clamp large enough to grip the door track and prevent the door from moving, a socket wrench or adjustable wrench to fit the bolts holding the spring, a ladder or step stool, safety glasses, and work gloves.

Wear long sleeves and avoid loose clothing that could catch on the spring or bolts. Keep your face and hands away from the spring at all times—a broken or slipping spring can cause deep cuts or broken bones. If you have never worked with high-tension springs before, consider watching a video of the process first so you understand the sequence.

Before you buy a replacement spring, measure or locate the specifications of your old one. Look for a label stamped or painted on the spring itself. If you cannot read it, measure the coil diameter (the width of the spring when coiled), the wire thickness, and the total length of the spring from end to end. Write these numbers down and bring them to a garage door supplier or search online for a spring that matches. Buying the wrong size or tension rating can make the door impossible to open or cause it to slam shut.

find the door and release the spring tension safely

Close the garage door completely and unplug the garage door opener from the electrical outlet. This prevents the opener from activating while you are working. Place the C-clamp on the door track just below the lowest roller on each side of the door. Tighten the clamp so the door cannot move up or down. Test it by trying to lift the door by hand—it should not budge.

Next, you need to release the tension in the broken spring. If the spring is already broken and hanging loose, tension may already be released. If the spring is still intact but you are replacing it as a preventive measure, you will need to wind it down. Locate the winding cone (the part with holes in it) on the end of the spring closest to the center of the door. Insert the winding bar into one of the holes and slowly turn it counterclockwise, moving the bar down to the next hole as the spring unwinds. Do this slowly and carefully—do not let the bar slip out of the holes. After a few turns, the spring should be fully unwound and safe to touch.

If you are unsure whether tension is fully released, do not proceed. A spring under tension can snap suddenly and cause injury. When in doubt, call a professional garage door technician.

Remove the old spring and install the new one

Once the door is clamped and tension is released, locate the bolts holding the spring to the mounting bracket. These are usually at the end of the spring closest to the center of the door. Use your wrench to remove these bolts and set them aside in a safe place. Carefully slide the old spring out of the bracket and set it on the ground away from your work area.

Slide the new spring into the same bracket, aligning the holes in the spring's end loop with the bolt holes in the bracket. Insert the bolts and tighten them by hand first, then use the wrench to snug them down firmly. Do not over-tighten—you just need them tight enough that the spring will not slip when you wind it.

Before you wind the new spring, double-check that the door is still clamped and that you have the winding bar in hand. The winding bar is your safety tool for the next step, so make sure it is within arm's reach and that you understand how to use it.

Wind the new spring to the correct tension

This is the most critical step. The spring must be wound to the exact tension rating for your door, or the door will not open and close properly. Most residential garage doors require between 200 and 400 turns of the winding cone, depending on the spring size and door weight. The label on your old spring or the documentation from your supplier will tell you the exact number of turns needed.

Insert the winding bar into one of the holes in the winding cone at the end of the spring. Turn the bar clockwise slowly and steadily, counting each full rotation. After each turn, move the bar down to the next hole to keep it find. If the bar ever feels like it is slipping or the spring is not turning smoothly, stop when ready and check that the bolts are tight and the spring is seated correctly in the bracket.

Wind the spring until you reach the specified number of turns. This usually takes 5 to 10 minutes of steady, careful work. Do not rush—a spring wound too tight will make the door hard to open, and a spring wound too loose will not support the door's weight. Once you reach the target number of turns, carefully remove the winding bar and set it down.

Test the door and check the balance

Remove the C-clamp from the door track. Plug the garage door opener back in. Stand to the side of the door (not directly in front of it) and use the opener button to open the door slowly. The door should rise smoothly and evenly without jerking or tilting to one side. If it tilts or moves unevenly, stop when ready and close the door. This usually means the springs are not balanced—one may be wound too tight or too loose.

If the door opens smoothly, let it open all the way and then close it. Listen for any unusual sounds like creaking or grinding. The door should move quietly and stop at the top and bottom without bouncing. If you hear grinding or the door bounces, the springs may need adjustment or there may be another issue with the door track or rollers.

If both springs were old, replace the second one now using the same process. This ensures both springs are new and will wear evenly, keeping the door balanced. If you replaced only one spring and the door still feels unbalanced after testing, the other spring may be near the end of its life and should be replaced soon.

Common mistakes to avoid

The most common mistake is trying to wind or unwind a spring without a winding bar, using your hands or pliers instead. This is dangerous—a slipping spring can snap and cause serious injury. Always use the proper winding bar and keep your hands and face away from the spring while it is under tension.

Another mistake is not clamping the door before you start. If the clamp is not in place and the spring suddenly releases, the door can fall and cause injury or damage. Always clamp the door first, even if you think the spring is already broken and harmless.

Buying the wrong spring size or tension rating is also common. Springs are not interchangeable—a spring that is too light will not support the door, and one that is too heavy will make the door hard to open. Always verify the specifications before you buy, and if you are unsure, ask the supplier to confirm the size matches your door.

Finally, do not skip the test step. Opening the door slowly and checking for smooth, even movement tells you whether the spring is wound correctly. If something feels wrong, close the door and investigate before using the opener repeatedly.

When to call a professional instead

If the spring is broken and you cannot safely release the tension, or if you are not comfortable working with high-tension springs, call a garage door technician. The cost of a professional replacement is usually between $200 and $400 per spring, depending on your area and the spring size. This is worth the cost if it means avoiding injury.

You should also call a professional if the door still does not move smoothly after you replace the spring, or if you notice other problems like bent tracks, damaged rollers, or a misaligned door. These issues can make the door unsafe to use and may require professional adjustment.

Frequently Asked Questions

How do I know if my extension spring is broken?

A broken extension spring will be visibly separated or hanging loose inside the frame. You may hear a loud bang when it breaks. The door will feel much heavier to open, or it may not open at all. If the door tilts to one side or moves unevenly, one of the springs may be broken.

Can I replace just one spring if only one is broken?

Technically yes, but it is not recommended. If one spring is old enough to break, the other is likely near the end of its life too. Replacing both at the same time keeps the door balanced and prevents you from having to do this job again in a few months. The extra cost of one more spring is usually worth the convenience.

What if I wind the spring too tight or too loose?

If the spring is too tight, the door will be hard to open and the opener may struggle. If it is too loose, the door will not stay up or will fall quickly. You can adjust the tension by unwinding or winding the spring a few more turns, but you must use the winding bar and follow the same safety steps. If you are unsure how many turns to add or remove, call a professional.

Do I need to replace the bolts when I install a new spring?

No, the old bolts are usually fine to reuse. However, if they are bent, stripped, or corroded, replace them with new ones of the same size. Use bolts rated for the tension of your spring—your supplier can recommend the right grade.

How long does a garage door extension spring last?

Most extension springs last between 7 and 12 years, depending on how often the door is used and how well the springs are maintained. A door used 4 to 8 times per day will wear springs faster than one used once or twice daily. Regular lubrication of the spring and hinges can extend the life of the springs.