According to Truetex.com, the average garage door springs can be expected to last about seven years. Once these springs fail, your garage door will no longer open and close properly until the springs are replaced. To ensure your repair will be successful, it's important to select the correct springs for the job. When choosing new springs for a garage door, consider such factors as size, design, handing and spring function to find the correct replacement parts.
Determine which type of springs you need for your door. Extension springs run along the tracks above your door and are aligned perpendicular to it. Torsion springs are situated directly above the door in a coil-type mechanism. Torsion-spring replacement is extremely difficult and potentially deadly, and is best left to professionals. It should not be considered a job for DIY homeowners.
Check the manual that came with your door if you still have it. The manual should contain information on replacement parts and recommended spring sizing. Those who no longer have the manual for their door will have to rely on other selection methods to choose the correct spring.
Examine the springs and other door components. Some springs are marked with sizing information. For example, a spring marked 225B24 has a wire size of .225 and is 24 inches long, according to Truetex.com.
Remove the spring and take it to a local garage door installer or parts supplier. Many dealers can help you identify the manufacturer and with ordering the correct replacement parts.
Measure the spring yourself to determine the correct size. With the spring in a relaxed state, measure the overall length. Then measure the length over a single section of 10 coils. Use this 10-coil measurement to determine the wire size for your spring using the chart at industrialspring.com. Finally, measure the diameter. For extension springs, you'll need the outside diameter; for torsion springs, you'll need the inside diameter.
Determine the handing of your spring. Hold the spring vertically in front of you. If the coils rise up to the right, you have a right-hand spring. If they rise up to the left, you have a left-hand spring.
Use the sizing, handing and manufacturer's information you've determined to order the correct replacement springs. You can find a list of garage door spring suppliers in the Resources section, or contact your door's manufacturer directly.