If you have ever installed a side mount jackshaft operator on a standard lift garage door you have probably experienced the cables coming off of the drums. This is an extremely common occurrence as shaft mounted openers are designed specifically for overhead doors using high lift kits. Standard lift setups lack the downward acting force required to maintaining cable tension. This causes the opener to temporarily jump upon starting. Garage door pusher springs come in 3 common sizes ( 9″ 15″ 27″). The different lengths are designed to be used with specific size doors and operators.
Pusher Spring 9″
The 9 inch pusher spring is best used on residential garage doors. Most shaft mounted residential operators by Liftmaster such as the model 8500 or model 3800 have built in cable tensioners. However, instance where tracks are out of level or old doors retrofitted with shaft operators might need additional assistance.