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Garage Door Opener Chain Adjustment

The chain on my garage door opener seems to be sagging and rubbing on the track. How do I adjust it?

There are only a few ways that the chain can be tightened.  There may be an adjustment linked to the chain, or an adjustment to the length of the door opener track.  Both adjustment types should be done with the door closed and disconnected from the opener using the emergency release.

Chain adjusts by shortening the chain itself...

Adjustments on the chain are located at or near the master link where the chain engages with the cable (graphic below left).  These usually consist of a bolt with two or three nuts, one or two for locking (or a nut and lock washer) and one for adjusting.  You loosen the locking inner nut, and turn the outer nut clockwise to adjust the excess slack from the chain.  Do not over tighten the chain! This will cause premature wear on the chain rollers.  Adjust it tight enough so that the center of the chain sags about 1/2" down from parallel with the track (graphic below right).

amp-img alt="Allowable chain sag on garage door opener" height="144" src="i/chainsag.gif" width="350" layout="responsive">

Chain adjusts by moving the opener trolley guide tube or rail...

The second adjustment is located on the top of the opener body.  This is common on the Stanley chain drives that utilize the tubular-style track (graphic below).  There is a bolt that is turned clockwise to actually extend the length of the track, thus removing the slack from the chain.  Same rule applies concerning recommended chain slack... don't overtighten the chain!! 

One thing about this second adjustment style is that, if the body of the opener is mounted in a very rigid fashion and has no "give", the tubular track will bend when you try to make this adjustment.  So, you might have to loosen the mounting bolts or make other adjustments to the mounting assembly to allow the adjustment.

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