Why did my garage door come off its track on one side only?
A door comes off on one side because something happened to that side alone: most often a vehicle bumped the door or the track, or a cable on that side snapped and let that corner drop while the other corner stayed up. Both sides are lifted by separate cables and ride in separate tracks, so a failure on the left has no effect on the right until the door goes crooked and binds.
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Once one side is out, stop using the door and leave it alone. A door out of its track is unstable and can fall, and running the opener again is what turns a repair into a replacement — the opener keeps pulling on a door that can no longer move straight, and panels, rollers, hinges and the track itself bend further with every try.
Why it happens on one side
Vehicle impact is the most common cause. A bumper tap at low speed bends the vertical track or knocks a roller out of it, and the door jumps the rail the next time it runs. The damage looks small from across the garage — a slight kink in the track, a roller sitting outside the channel.
The second most common cause is a snapped cable. The cable on each side carries that side's share of the door's weight down to the bottom bracket. When one breaks, that corner drops fast, the door racks into a diamond shape, and the rollers on that side pull free. If you can see a cable hanging loose or coiled on the floor, that is almost certainly what happened.
After that come worn or broken rollers, a loose or pulled-away track bracket, a bent hinge, and something left in the door's path — a trash can, a ladder, a bike — that stops one corner while the other keeps going. Unbalanced springs make all of these more likely, because a door that is heavy on one side wears that side's rollers and track harder.
What you can check yourself
- Unplug the openerPull the opener's plug so nobody hits a remote or wall button by habit. That single step prevents most of the extra damage that happens after a door goes off track.
- Look for a loose cableFrom a safe distance, look at the cable running down each side of the door. A cable hanging slack, coiled on the floor, or wrapped oddly around the drum tells you why that side dropped. Do not touch it or try to put it back.
- Look at the track and the rollersCheck whether the vertical track is bent, dented or pulled away from the wall, and whether any rollers are sitting outside the channel. Note what you see so you can describe it on the phone.
- Check for an obstructionLook along the floor and the door opening for anything the door could have caught on. Finding it explains the failure, but it does not make the door safe to run.
- Leave the release cord aloneDo not pull the red release cord on a door that is crooked or hanging. Disconnecting the opener on an unbalanced door can let it drop.
When to call a technician
An off-track door is past DIY from the moment it happens. The door has to be secured and supported before anything is touched, and the rollers, cables, drums and springs all have to come back into balance together — a door put back on the rail without re-tensioning and re-squaring will come off again. Never attempt spring, cable, drum or bottom bracket work yourself; those parts hold the door's weight under tension.
Whether garage door repair needs a state contractor license varies by state, and many states leave it to the city or county. The technician holds whatever license their state requires, and your state's contractor licensing board is the place to verify it. A repair like this almost never needs a building permit; a full door replacement does in some cities, so ask your local building department before ordering a door. We can arrange a visit with an independent local garage door technician — the estimate is free, and the technician gives you the price before any work starts. Call (866) 394-4210.
What the technician will do
- Secure the door firstBefore anything else, the door is blocked and supported so it cannot drop or shift while the work is done.
- Replace damaged rollers, hinges and trackBent track sections, flattened rollers and cracked hinges get replaced rather than straightened, because reused parts are what cause a second derailment.
- Re-string cables and re-seat drumsThe cables are re-run and the drums re-seated so both sides wind evenly and lift the same amount.
- Re-square and rebalanceThe door is brought back to square, spring tension is checked against the door's actual weight, and the balance is set so neither side carries more than its share.
- Cycle testThe door is run up and down by hand and on the opener, with the safety reverse and sensors checked before the technician leaves.
Related questions
- Can I just lift the door back into the track myself?
- No. The door is unstable and heavy, and the cables and springs are still under tension even when the door looks limp. Forcing it back usually bends more track and can drop the door.
- The door looks fine now that it settled — can I use it once?
- Don't. A door that has jumped the rail is no longer square, and one more cycle on the opener is what commonly turns a roller-and-track repair into panel damage. Leave the opener unplugged until it is inspected.
- Does one side coming off mean the whole door is ruined?
- Usually not. If it was caught early, the repair is normally rollers, hinges, a track section and cables. Whether panels are replaceable depends on how far the door bent and whether that model's panels are still made.
- What does this repair cost?
- It depends on the door's size and weight, which parts failed, whether replacement parts for that model are still made, how the garage is accessed, and what the technician finds once the door is secured and inspected. The estimate is free and the technician gives you the price in person, for your approval, before any work starts.
- How do I stop it happening again?
- Have the balance and the roller condition checked rather than only putting the door back on the rail, and keep the area in front of the door clear. Most repeat derailments trace back to worn rollers, a loose track bracket, or springs that were never rebalanced.
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