Quad Spring Replacement

Garage Door Torsion Springs are normally centered above the garage door on a one inch shaft. ... The shaft running through the springs transfers tension from the springs to the cable drums at the end of the shaft. These drums pull on the cables, which pull on the bottom of the door to balance the weight of the garage door.
 
With a Quad spring system, there is a center bracket that connects two of the springs together, which turns the 2 springs into one and then another center bearing plate doing the same for the other 2 springs. Usually only one or 2 of the springs will break, however, replacing ALL springs is HIGHLY recommended as the other spring/springs will break very soon after, ultimately costing you more money than if you changed them all at the same time. 
 
Price Veries depending on the size of the springs.