Uneven (jerky side to side) closing

[EMB]

7 ft high by 9 ft wide, 4 panel metal garage door with a Chamberlin 1255LM opener. The springs are on either side attached to the door with cables and pulleys.

Our door started to jerk from side to side as it was going down, sometimes stopping. Opening seems smother but not quite as smooth as the other door. I let this go on for too long (head in the sand). The gears in the opener failed. I replaced the gears and the opener works well but the door still jerks from side to side on the way down. I have greased the rollers and track and have inspected the rollers and rails for damage. I exchanged the two springs from the smooth operating door with the jerky one but this did not help.

Any ideas would be most appreciated.

[homerepairguy]

First disengage your opener from the door by pulling the cord from the track. Move your door up and down. Is it still jerky? If it can't go up smoothly the opener won't do any good. More than likely if it is jerking that implies uneven tension being exerted on both sides of the overhead. One side is pulling harder and "wedging" the door until the other side equals this out (temporarily) and on and on it goes. The sides need to have even pressure exerted. Once the door is properly adjusted then the opener ca be hooked back up. Usually openers only mask the problem before it sometimes becomes too late.

[EMB]

You say the pressure must be equal on both sides. That makes sense to me, but how do you adjust the pressure and how do you tell if the pressure is even. I have tried installing new springs and also used the springs from another identical door that was working fine. Neither the new springs or the switched springs helped.

[homerepairguy]

There are 2 types of springs- extention and torsion. Extension are singles or doubles on each side track for the door. They are rated and usually color coded on the ends for the appropriate spring (ie green, red, black, etc.) The total weight of the door is evenly dispersed among the number of springs. The tension or pull on the spring is determined by the length of cable attaced to the spring(s). If the sides are not equal one side will pull quicker, it should be obvious which side goes up first. Lengthen that cable or shorten the slower to respond side. Sometimes this takes several attempts until it equals itself out. If the springs aren't matched this may not be possible. A green on one side will not match a red on the other. Torsion usually aren't a problem because the pair of cables are made to a specific length. They either have enough tension or don't. Either way the springs are to take the door up, NOT the opener. The opener is an initiator not a pulling device. It also controls the even speed ascent of the door.

[HayZee518]

check the alignment of the tracks. over time the garage shifts just like a house settles. the tracks have to be parallel with each other and plumb.

[gdoorpro]

If the rollers are fine and the springs are fine. It usually turns out to be the 3" pulleys. You should have two stud pulleys and two saddled pulleys. They wear out and need replaced after 10 years or more. They are cheap. check it out.

[EMB]

Thanks to all, but especially to gdoorpro. It turned out to be one of the fixed pulleys. A simple $4.50 repair.

[gdoorpro]

Your attitude of gratitude is much appreciated.
Ryan