Sectional Garage Door Extension Springs

Extension springs for standard sectional garage doors

On this page you can learn more about extension springs, determine what replacement extension springs you need, and see how to order springs.

Determining Which Extension Springs to Order:

Learn About Extension Springs:

Important Links for Extension Spring Doors:

Introduction to Sectional Garage Door Extension Springs

Extension springs have four characteristics: length, inside diameter, wire size, and type of end. Even though all springs have these properties, every manufacturer has its own design for making springs. As a result the dimensions on the springs you receive may be different from the original springs on your door.

The most important property of an extension spring is its pull, the amount of weight it lifts when stretched. Most residential springs are manufactured with lifts in 10 pound increments. Extension springs for heavier commercial and industrial overhead doors are generally made with lifts in increments of 20 pounds.

Definition: Extension Spring System
A set of extension springs on each side of a door connected with pulleys and cables to counterbalance the weight of the garage door. Most doors only have one spring on each side of the door, but often there are two on each side.

If there is one extension spring on each side of the door, the spring on each side must lift 1/2 of the door weight. On a 100 pound, for example, the spring on each side will lift 50 pounds. However, because the spring is pulling a pulley instead of the cable, only half the tension from the spring is transferred to the door; the other half is transfered to the other end of the cable where it is secured with a cable clip and an s-hook. As a result, the 100 pound door in our example needs a 100 pound lift spring on each side of the door.

Extension Spring Counterbalance

Garage door springs counterbalance the weight of garage doors to make them easy to open and close. On a sectional door extension springs stretch as the door closes. For this reason they are also designated stretch springs.

When a garage door is open most of the door weight is stored in the horizontal tracks. The door will stay open without being supported because the springs counterbalance the weight of the door with cables and pulleys. One end of the cable on each side is connected to the bottom of the door. The cable runs over the stationary pulley, onto the pulley which is attached to the extension spring, and then back to the horizontal track angle where it is secured with a cable clip and s-hook.

The standard spring for a 7’ high door is 25” long. When the door is open, the spring pulls on the pulley which supports the cable to hold the door open. One end of the cable supports the bottom of the door; the other end of the cable pulls on the s-hook which is secured to the horizontal track angle. At this point there is no stretch on the 25"springs.

As the door closes the spring stretches and the door weight transfers from the horizontal tracks to the cables which are attached to the bottom of the door. This weight causes the springs to stretch, but on a balanced door the pull on the springs and cables match the door weight

On a 200 pound door with two springs, for example each spring pulls 200 pounds or a total of 400 pounds when fully stretched. When stretched only halfway, the two springs pull only 200 pounds. However, because one end of each cable is attached to the bottom of the door and the other end is connected to the horizontal angle, the cables on both sides are pulling a total of only 100 pounds, or 50 pounds on each side

When the door closes half way, the cable extends half the door height, but because of the pulley system, the springs stretch only ¼ of the door height or 21 inches. The total length of each spring at this point is the original 25” plus the 21” of stretch, or a total length of 46 inches.

When the same 200 pound door is fully closed, one end of the cable extends half the door height, but because of the pulley system, the springs stretch only 1/2 of the door height or 42 inches. The total length of each spring at this point is only the original 25” plus the 42” of stretch, or a total length of 67 inches.

Each spring is pulling 200 pounds, or a total of 400 pounds, but because the cable travels around the pulley, half the pull is on the bottom of the door and the other half of the pull is on the opposite end of the cable attached to the horizontal track angle which is fixed and does not move.

Temporary Fixes for Broken Spring Ends

Quite often the loop breaks off the end of an extension spring. There are two options for fixing the spring without replacing it, or for making your door operational until springs can be ordered. One is to separate the last two coils with a screwdriver and attach the s-hook or eye bolt.

The other temporary fix is to install a clip at the end of the spring. You can buy these at our extension spring hardware page. Bear in mind that these are temporary fixes. You can expect your spring to break again at the other end or at another place along the length of the spring. The only reliable repair is to replace both or all four springs.

Determining Which Extension Springs You Need

It is important that you replace your old extension springs with new springs that will properly match your door weight. This will provide you with a properly balanced garage door, one that will stay on the floor when it is closed, stay halfway, and stay up when you open the door. The blog is written for torsion springs, but testing the balance of a door is the same for both systems. Broken pulleys and cables frequently accompany broken extension springs, so you may have a slightly bigger project on your hands that you anticipate.

Making Measurements

There are three important pieces of information that you will need to get in order to select the proper springs for your garage door. These are the manufacturer and model number if you can find them; if not you will neeed to determine the total door weight. You will also need to measure the door height and the spring length.

Weigh your garage door on the side that is broken
One method for weighing a 16' or wider door is to slide your scale under the end of the door on the side that has a broken spring. Raise the other side to the same height and then support it to keep the door level.
The door weight can be difficult to calculate. You must use an analog scale, as most digital scales do not respond to a change in the door weight when rollers no longer stick to the track. If you have two broken extension springs, slide an analog scale under the center of the door to get the total weight. If one of your two extension springs is broken, slide the scale under the door on the side with the broken spring as pictured to get half the weight.

Shake the door and check each of the rollers for binding. If one spring is broken, the weight you read off the scale at the broken will be 1/2 the door weight. If both springs are broken, the scale will read the total door weight. For more information, see the first five steps of our Extension Spring Replacement tutorial.

If you have two springs on each side of your door, open the door, remove the second spring on the side with the broken spring, and lower the door onto the scale on the side with the broken and removed spring. Double this weight to determine your total door weight. Remember that since you can't weigh the door at the very end you, and if the center of your scale is 12" from the very end, you will need to add to the weight your scale shows. A percentage determined by dividing 16' by 15' arrives at 106.66% per cent. Hence a weight of 100 pounds X 106.66% = 107 pounds. Double this and the total estimated door weight should be around 214 pounds. This door would use two 210 pound lift extension springs.

A more accurate method for weighing either a torsion spring door or an extension spring door is on our YouTube channel.

The door height also helps to determine which springs you need. For example, the extension springs made for 14' high doors are intended to stretch twice as far as the springs made for 7' high doors. As a result, the un-stretched length of an extension spring generally increases as the door height increases.

Another measurement you will need to make is the un-stretched spring length, not including the ends. Extension springs tend to stretch over time so you will need to compress the coils when measuring the length. You may need to insert a shaft in the middle of the spring to keep it straight while compressing the coils. Some springs are ruptured so badly you may need to measure and count coils to calculate the length.

While the door industry has standardized on spring lengths, there are multiple spring lengths for some of the more common door heights.

If you decide to purchase an extension spring with a shorter un-stretched length than your old spring, you will need to adjust your cables. There will need to be 2" of additional length for every inch that your new spring is shorter than the old spring. If your cables are not adjustable or are too short, you will either need to replace the cables or order a longer spring. If you need a spring with dimensions not listed in our parts catalog, we can order a custom spring. These generally cost about 50% more than our standard springs, so it is probably better to change the cables instead.

If your new spring is longer than your old spring, you will need to adjust the cables to shorten the pull. Sometimes this requires mounting the S-hook on the new springs closer to the garage door.

It is also helpful to examine your spring for color codes. The lifts for extension springs follow these colors:

  • Tan - 100#, 200# & 300#
  • White - 110#, 210# & 310#
  • Green - 120#, 220# & 330#
  • Yellow - 130#, 230# & 330#
  • Blue - 40#, 140# & 240#
  • Red - 50#, 150# & 250#
  • Brown - 60#, 160# & 260#
  • Orange - 70#, 170# & 270#
  • Gold - 80#, 180# & 280#
  • Light Blue - 90#, 190# & 290#.

This pattern is repeated through all the lifts.

Types of Extension Spring Ends

Various styles of extension spring ends
From front to back: Open ends, double-loop ends, and clipped ends. There are three types of ends on extension springs and each of the springs has their own advantages and disadvantages.

Open looped ends are the easiest to replace. You will not need to open the eye-bolt, and you will not need to disassemble the pulley. One disadvantage, though, is that the whole spring relies on open wire at the end. If this is the only part of your spring that breaks, you may be able to save a few dollars and some time if you put a clip on the end of the spring as we show above.

Double looped ends are more sturdy than open loops, as there are two coils of the spring that connect to the eye-bolt and the pulley. One disadvantage, though, is that they take longer to replace.

Clipped ends are even more durable than double loops. The spring clips put less stress on the spring ends to help lengthen the life of the spring. These come standard on extension springs for doors that weigh 200 pounds or more. The disadvantage, though, is that they can be more difficult to replace.

Replace One Spring or Two?

We recommend that you replace all of the extension springs on your door. As the springs fatigue, they loosen and do not provide as much lift as the new spring. If you only replace one of two springs, the door may open unevenly and cause problems such as binding or rollers coming out of the tracks.

Cables & Pulleys

Replace worn pulleys when you change your old extension springs
Worn pulleys can cause problems, and it is good to replace them while you are changing your extension springs.

Extension spring pulleys wear out frequently and sometimes they need to be replaced at the same time as the springs. We highly suggest that you check the status of your four pulleys. Since each pulley on your door experiences about the same amount of wear each time the door opens, we suggest that you replace all four of your pulleys if you find one that is worn. This will also save you time in the future and it will save on shipping costs.

Extension spring cables cables wear out very often with the springs. If you examine your cables right now, you may not see any problems. Many times, though, the cable is frayed or worn in the cable clip, and the cables need to be replaced. This is something to consider when looking to purchase new extension springs.

We suggest that you replace both cables. Even though one may not be worn out, it will save you the trouble in the future. The prices for the cables for other door heights are determined by the length of cable needed.

Safety cables are very important to have on extension spring doors. You typically will not need to replace these cables, but if you do not have them, you should consider purchasing them. The cables run through the length of the spring and contain the pieces of the spring when it breaks. These protect people from injury or death, and they protect cars and other valuable items from being damaged when the spring breaks.

All of these parts and more can be purchased on our extension spring hardware page. See our how to order section below for help purchasing your extension springs.

How to Order Springs

Notice below the two tabs for selecting extension springs.

Order by Door Weight. If you know your door weight, click the "Find by Door Weight" tab. You will then select the number of springs on your door, the door height, the spring length, and the door weight.

After you click "Go!" a new page will appear with up to three options for spring ends: open loops, closed double loops, and clips. You'll also see the spring part number, length without the end loops or clips, the spring weight, and the lift or pull of each spring. You'll also see the unit price of each spring. If you have more than one door you can save on the price of the springs as well as on the shipping cost. If a long life spring is available it will appear below the first option or options above.

Next, you can then click the part number for more information, and then click "Add to Cart." Or, you can simply click the "Buy" button and then follow links to purchase the springs.

Order by Model Number. Most of the newer garage doors have identifying stickers that designate the manufacturer and model number. If you have this information, click the "Find by Model Number" tab.

You will then enter the manufacturer, model number, door dimensions and additonal information to help you order the correct springs. Click "Go!"

After you click "Go!" a new page will appear with up to three options for spring ends: open loops, closed double loops, and clips. You'll also see the spring part number, length without the end loops or clips, the spring weight, and the lift or pull of each spring. You'll also see the unit price of each spring. If you have more than one door you can save on the price of the springs as well as on the shipping cost. If a long life spring is available it will appear below the first option or options above.

Next, you can then click the part number for more information, and then click "Add to Cart." Or, you can simply click the "Buy" button and then follow links to purchase the springs.

One Final Note. In the early decades of door manufacturing springs were often much larger than the standard extension springs made today. Older springs also fatigue and grow in length. As a result your new extension springs will likely look different then your old springs. This is normal, and, assuming that your new springs are for the same door height and have the same pull as your old ones, you can expect them to be fully compatible.

Find My Sectional Extension Spring

Note: The spring options given are based on original door weights. Hurricane bracing, decorative hardware, and other additions to the door may alter the door weight, rendering the suggested springs unuseable.

The model number search does not cover all door heights. If your door height is not given, please use the "Find by Door Weight" tab.

If you want us to check your calculations before ordering, you can contact us with your door weight, the total number of springs on the door, or any door information such as manufacturer and model number that you can find.