Pusher spring bumpers help the garage door start down into the opening by pushing against the top section. They are most often used in applications with a side mount jackshaft opener to prevent cables from slipping off the drums.

The main purpose of spring pusher installation is to assist in maintaining constant cable tension when the door is starting the down cycle. This is especially the case on doors that lack a downward acting force achieved with highlift or full vertical lift track. When an opener starts running with the door in the open position there is a tendency for the door to initially jump – causing cables to be thrown of the drums.

Jack shaft operators installed on standard lift doors are especially prone to cables being thrown off the drums because they lack a natural downward acting force.

Another benefit of pusher springs is the prevention of the door flying off the back end of the horizontal tracks in the event of user or operator error.  This is especially the case on manually opened and closed doors where the user might fling the door open with excessive force. This problem is quite common in loading dock bays and storage facilities where people fling the door upward as fast as they can.

Do I Need Pusher Springs or Track Bumpers?

Spring pushers are often called push down bumpers, not to be confused with a different part called a leaf bumper. Unlike leaf style bumpers, pushers are spring loaded. As the door travels up the top panel pushes against the pusher spring causing compression. Then when the door starts downward travel the pusher springs exert force against the top panel, avoiding the sudden jump at the start. This is usually enough to keep the cables from slipping over the grooves of the drum. Many people get pushers and bumpers confused although they are closely related.


  • Pusher springs are installed at the back of the horizontal tracks compressing against the top section as the door opens. When the door starts closing that tension is slowly released to prevent the sudden jump start that causes cables to slip off the drums. These parts are often referred to as plungers or stoppers.
  • Leaf bumpers also mount at the end of the horizontal or vertical garage door track. Unlike pusher springs that compress as the  door opens, bumpers don’t move. The primary purpose of the bumpers are to keep the door from opening too far. This is common in settings where users fling the door open quickly. Some examples would be storage units and loading docks where doors need to be quickly opened.

Parts of Pusher Springs

Spring – 30lb, 60lb,150lb Compression Options

Rod – 1″ Diameter Galvanized 27″ , 15″,  9″ Options

Rubber Bumper – 2″ Diameter Rubber Stop

Mounting Bracket – 12 Gauge Galvanized With Adjustable Groove Placement

Mounting Hardware – (2) 3/8″-16 Hex Bolts (2) 3/8″-16 Hex Nuts (Flat Washers Optional)


Choosing The Correct Size & Compression

Selecting the correct size pusher is important to get your door running smoothly. Installing a push down bumper that is too strong could damage your garage door opener. For example, using the 27″ spring pushers on a residential door with an 8500W would cause excessive wear as the 27″ pushers have 150lbs of force per pair. The pushers should match the door and opener size and should be adjusted further or closer from the top panel when the door is in the open position.

Side mount jackshaft openers like the Liftmaster MJ5011 & J5011 operators are not designed to be installed on doors that lack a downward acting force. In plain terms, if you don’t have high lift or full vertical lift track your warranty will likely be voided if you install the operator on a standard lift door. With that being said most people still install them anyways and quickly discover that their garage door cables frequently get thrown off the drums rendering the door unusable.


Pusher Spring Length, Compression & Rating

9″ Pusher Springs (Pair)3" Travel30lbsResidential - 3800, 8500W Operators
15″ Pusher Springs (Pair)6" Travel60lbsCommercial - MJ5011 Operators
27″ Pusher Springs (Pair)15" Travel150lbsCommercial - J5011+ Operators
Leaf Bumber (Pair)N/AN/AAll door & openers


Pushers For Liftmaster 3800, 8500W Cable Tension Monitors (41A6104)?

Yes, pusher springs are frequently used with the Chamberlain Liftmaster side mount jack shaft opener models 3800 & 8500W. These models come with a built in device called a Cable Tension Monitor (41A6104) , although medium duty and full duty openers don’t come with this part.

As the name says this device monitors cable tension with a small lever that maintains contact throughout the opening and closing cycle. The part connects directly into the liftmaster residential openers allowing for real time adjustment. Even with this device installed and configured it is still often necessary to install the 9″ residential pusher springs for standard lift doors. Chamberlain Liftmaster acknowledges that pushers are often needed if the opener forces can’t be adjusted to fix certain issues.


Pusher Spring Installation

Pusher springs are sold in pairs with a right and left side mount. The brackets attached to the springs are mounted at the outside ends of the horizontal tracks using track bolts & nuts. In the rare case of the horizontal track being too short a piece of angle iron can be added to the end of each track with the pushers being mounted to the punch angle. The pushers should always be mounted at equal distances to ensure that balanced for is applied to the top section of the garage door.

Here are a few key points to keep in mind when starting installation:

  • Size your pushers according to the door size & opener strength.
  • Pushers should be installed on the outsides of the horizontal track.
  • The full travel and compression rating doesn’t have to be used even though it is best practice.
  • Using too strong of pushers will wear out your opener over time.
  • If preventing cable slipping during the down cycle is needed pushers should be used.
  • If the goal is only to stop the door from coming out of the tracks bumpers should be used.


Pusher Spring DIY Instructions

  1. Pushers are sold in pairs with a right and left side mount. The brackets mount to the outside of the horizontal tracks and angle inward. Identify your right and left side pushers
  2. Using a pair of vise grips or C-clamps temporarily mount the pushers as far back on the tracks as possible with the rubber stop end facing the door.
  3. Raise the door to the open position aligning the rubber stop end of your pusher with the top corner of your door.
  4. Repeat the the same process on the opposite side using the exact length spacing for balance.
  5. Chances are the end of track positioning won’t be correct so your will need to move the pushers further up the track for the right amount of pusher compression.
  6. Measure the amount of compression with a tape and adjust accordingly keeping in mind the compression rating for the pushers you purchased.
  7. Once you have the right distance and alignment you can mark the hole locations. You will need to drill 2 or more holes for your fasteners to mount to.
  8. Fasten the pusher to the horizontal tracks with 3/8″ track bolts & nuts.
  9. You can expect the spring pushers to be noisy during operation so be sure to lubricate each of them.


Additional Troubleshooting Options…


Horizontal Track Slope Adjustment

If after installing and adjusting the pusher springs you still have the reoccurring problem of cables slipping off the drums a few extra options exist. If your horizontal tracks have been installed level you may consider adding a slight down slope of 3″-4″ on each side. Creating a slight down-sloping track angle could help the force of gravity push down on your door section around the track radius.

The radius of the track itself with 10″ Radius, 12″ Radius and 15″ Radius being most common. The higher the radius the more gradual the curve of the track. 15″ Radius track results in much smoother door operator as the door curves down into the opening

Spring Adjustment Balance Test

With your opener disconnected and the door in the closed position you can perform a  balance test. Raise the door manually about half way open. At this level the door should sit in the opening without moving up or down. If it begins drifting too far up or down you can be sure that your door isn’t balanced. Drifting up implies the springs are running “hot” while drifting down implies “cold” or “heavy”.

Initially most people install torsion springs “hot” meaning they add slightly too much tension in order to make the door easier to open by hand. However, running your springs hot isn’t necessarily the best option with jackshaft openers. This is the one circumstance where you would want to door to run on the heavier side – allowing the door to drift slightly lower to take advantage of gravity.

Cable Loose Slack

Torsion cables should be taut on each side of the door like a violin string. If one or both cables have slack with the door in the closed position that is a sign of a door installed out of alignment, slipped drums or improperly configured torsion springs. If at any point during door operation the cables get loose something is wrong.

Garage Door Guide Cal
Hello, I’m Cal – owner of Garage Door Guide LLC    

I write tutorials about garage door repair, installation and maintenance. With over a decade of experience in the overhead door industry I’ve learned a lot and I’d like to share my knowledge with you.

4 thoughts on “Pusher Springs: Stop Jackshaft Openers From Throwing Cables

    • Garage Door Guide says:

      No they aren’t necessary, but depending on the door configuration they could be useful.

      Most cables come off the drums due to issues with improper door (spring) balance. The second most common issue is setting the door down on top of an obstruction. If cables are popping off the drums with a chain hoist there are bigger issues with the door.

      Do you mean a jackshaft opener with a built in chain hoist like a JH5011 operator OR just a plain hand operated 4×1 RDCH?

  1. Scott Powell says:

    I am using the Liftmaster 8500w on a 12 x 7 double skinned insulated door(180.8 lbs). The opener is mounted on the right side of door. It has not thrown a cable yet but when the door is fully opened the left cable has slack. Door is level and installed correctly. Why am I having the issue and would pusher springs solve this problem. Any info would be appreciated. Thank you.

    • Garage Door Guide says:

      Without inspecting the installation its hard to say what the issue is but here are a few possibilities. A good starting point is to check the cables when the door is in the fully closed position… are both sides of cable (equally) tight like a violin string with the door closed?

      A reasonable fix for this would be to reset the cable/drum on the left side only before you try installing pusher springs. This can be very dangerous so consider hiring someone to do this. If both sides had slack in the cables then pusher springs would definitely be the answer…however with only one side cable loose I’m not so sure.

      It sounds like you are being proactive realizing that eventually that left side will probably throw cables in the future. The 8500w works best when the door has a downward acting force. If the door is opened too far on the open cycle vs slightly hanging down in the opening it loses the downward acting force that keeps the cable tension correct. That is what the pusher springs help with.

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