A commercial overhead door that lifts crooked—where one side rises faster or higher than the other—is almost always caused by a lifting cable that has slipped, frayed, or broken on one side. This creates uneven tension, tilting the door panel as it moves along the tracks. The door may bind, scrape the frame, or stall mid-cycle, often accompanied by a sharp pinging or scraping sound from the affected side. This is not a minor alignment issue; it’s a symptom of lost mechanical balance that can worsen quickly and risk cable failure or door collapse.
How Lifting Cables Maintain Door Balance
Lifting cables on a commercial overhead door run from the bottom bracket on each side of the door, up to the cable drum attached to the torsion spring shaft. As the springs unwind during opening, they turn the shaft, which winds the cables onto the drums, lifting the door evenly. Both cables must wind and unwind at the same rate to keep the door level. If one cable loses tension—due to fraying, slipping off the drum, or breaking—the door tilts because the intact side continues to lift while the damaged side lags or drops.
Visual Signs of a Cable Problem
Inspect the door while it’s closed and again while opening slowly. Look for gaps between the door and the floor on one side, or the door appearing skewed in the opening. Check the cables where they attach to the bottom brackets—fraying, rust, or broken strands are visible signs. On the cable drum, look for loose wraps, overlapping cables, or a cable that has jumped out of its groove. A crooked lift often shows one cable hanging slack while the other is taut.
What the Door Sounds Like When Cables Fail
Listen during operation. A healthy door operates with a smooth, steady roll. A failing cable may produce a sudden *ping* or *twang* as a strand breaks, followed by uneven movement. You might hear scraping if the door binds against the jamb or rollers jump the track. Intermittent clicking or slipping noises near the cable drum indicate the cable is not seating properly and may be about to jump or unwind unevenly.
What You Can Safely Check Yourself
You can visually inspect cables for wear, check bottom bracket attachments for looseness, and observe door travel for unevenness—all with the door fully closed and locked out. Never attempt to adjust cables, drums, or springs while the door is under tension. Do not loosen set screws on the cable drum or try to rewind a slipped cable. These components store dangerous energy; a sudden release can cause severe injury.
When This Requires a Technician
Any sign of cable fraying, broken strands, slipping on the drum, or uneven lift means the door is unsafe to operate. Technicians will release spring tension using proper winding bars, inspect the entire lifting system, replace damaged cables with aircraft-grade galvanized steel of the correct diameter, and re-seat cables evenly on the drums. They will also check drum wear, shaft alignment, and spring balance to prevent recurrence. This is not a lubrication or alignment tweak—it’s a tension-critical repair.
Frequently Asked Questions
Can I just tighten the loose cable to fix the crooked lift?
No. Tightening a cable without addressing the root cause—such as fraying, drum damage, or uneven winding—can create false tension and increase the risk of sudden failure. Cables must be replaced in pairs and wound with equal tension using calibrated tools.
Why did only one cable fail if they’re the same age?
Slight differences in lubrication, moisture exposure, or contact with hardware can cause one cable to corrode or fatigue faster. Doors that bind slightly to one side also place uneven load on the cables over time.
How often should lifting cables be inspected on commercial doors?
At minimum, inspect cables quarterly as part of routine maintenance—look for wear, corrosion, and proper seating on drums. In high-cycle or harsh environments, monthly checks are advisable to catch early signs of fraying or corrosion.
