When a commercial overhead door starts to close but then reverses before reaching the floor, the issue is often traced to the door’s strut system or its interaction with safety circuits. This reversal is typically triggered when the door’s closing force exceeds a threshold, prompting the operator to interpret the resistance as an obstruction—a safety feature designed to prevent crushing injuries or property damage. In the case of strut-related problems, the door may bind or drag unevenly during travel, creating false resistance that trips the reverse mechanism. Understanding the physical interaction between the struts, tracks, rollers, and operator settings is key to diagnosing whether the issue is mechanical or electrical in nature.
How Struts Function in Commercial Overhead Doors
Struts are vertical or diagonal reinforcement members attached to the back of door panels, especially on wide or high-lift doors. Their primary role is to prevent panel flexing under wind load or during operation, maintaining alignment between the door and the track system. On sectional doors, struts are typically mounted vertically and tied into the door’s reinforcement system, ensuring that each panel remains flat and moves uniformly. When struts become loose, bent, or detached, the door panel can warp or rack slightly as it moves, causing rollers to bind against the track or hinges to shift out of alignment.
This misalignment increases drag during closing, which the door operator interprets as an obstruction. Modern operators use either torque monitoring or door travel time to detect excessive resistance. If the door takes longer than expected to close or draws more current than normal, the system assumes something is blocking the path and initiates a reverse cycle. Strut-induced drag mimics this condition because it adds mechanical resistance without triggering the photo-eye or edge sensors.
Common Strut-Related Failure Modes
One frequent issue is strut detachment at the panel brackets. Over time, vibration and cyclic loading can loosen bolts or fatigue the metal at connection points. When a strut pulls away from the door panel, that section loses rigidity and may bow inward or outward during travel. This creates a visible ripple or twist in the door as it closes, often most noticeable in the middle panels of wide doors. You might hear a creaking or groaning sound as the panel flexes, followed by the door stopping and reversing.
Another failure mode is strut bending due to impact or improper reinforcement. If a forklift or vehicle strikes the door, struts can bend permanently, altering the door’s geometry. Even a slight bend can cause rollers to climb or jump the track, especially in the vertical or radius sections. This mechanical interference increases closing resistance and trips the reverse logic.
Corrosion is also a concern in coastal or humid environments like Metro Vancouver. Steel struts can rust at connection points or along their length, weakening the structure and increasing friction where they contact other components. Rust buildup between the strut and track or roller assembly can create a grinding sensation and audible squeal during operation.
What You Can Safely Check Yourself
Before calling a technician, there are several visual and operational checks you can perform without disassembling or tensioning any components. First, operate the door manually (after disconnecting the operator) and observe its movement. Look for any twisting, bowing, or uneven travel in the panels. Pay close attention to the mid-sections of wide doors—these are most prone to strut-related flex.
Inspect the struts for visible damage: gaps at mounting brackets, bent sections, or heavy rust. Check that all bolts are present and snug (but do not over-torque, as this can strip threads or crack brackets). Listen for unusual noises during manual operation—creaking, groaning, or grinding often indicates binding or flex.
Verify that the photo-eye sensors are aligned and clean, and that the bottom edge seal is not folded or damaged, as these can also cause false reversals. However, if the door reverses consistently at the same point in its travel—say, halfway down—and manual operation reveals panel distortion or binding, the strut system is a likely culprit.
When DIY Ends and Professional Service Begins
Tightening loose strut bolts or replacing obviously damaged struts can be within the scope of a facility maintenance lead, provided the door is fully secured and the operator is disconnected. However, any work involving the door’s structural integrity must be approached with caution. If struts are bent, cracked, or show signs of fatigue failure, replacement should follow manufacturer specifications to ensure proper load distribution.
More critically, never attempt to adjust or remove components connected to the torsion spring system, including the spring shaft, cable drums, or bottom brackets. These components store potentially lethal energy and require specialized tools and training to service safely. If your diagnosis points to issues beyond the struts—such as spring imbalance, cable wear, or operator torque settings—it’s time to involve a qualified technician.
A commercial door technician will assess strut condition, check panel alignment, verify operator sensitivity settings, and test the entire safety circuit. They may recommend reinforcing the door with additional struts, replacing damaged hardware, or adjusting the close force and travel limits to compensate for minor drag—though the latter is only a temporary fix if the underlying mechanical issue isn’t addressed.
