We always recommend the 2-spring system. Not only does it allow your springs to last longer, but it reduces the overall risk of your garage door going down.
Please fill out and submit the following form using the dimensions for the spring that you have. Then, we will calculate the dimensions for your new 2-spring system.
If you need help or aren't sure of the measurements of your current spring, start here: http://www.garagedoornation.com/pages/how-to-measure-springs
Please make sure to be as accurate as possible with your 1-spring measurements as it will increase accuracy for converting to 2-springs.