The new spring s diameter length and wire size or gauge must be the same as your old spring.
How to fix a garage door extension spring.
Slide a grocery bag or piece of cardboard behind the spring to protect the garage door.
Loosen the unbroken spring.
How to repair garage door springs and cables lock down the door.
The easiest way to do this is to take the broken spring to a local garage door dealer or home improvement center so they can help you find an exact match.
Clamp a locking pliers or a c clamp to the track just above one of the rollers.
A garage door weighs tans and it would be close to impossible to move it shut and open without the help of the door springs.
Spray each spring with garage door lubricant.
Wipe off any excess then repeat the process on the other side.