Well I did this experiment, sort of, I put the door all the way up unlatched it, got the stepladder and put vise grips on the pipe on the opposite end from the opener, but all that did was move the door back and forth, so my son said put the vise grips on the pipe so that it rest against the wall, then he took a long stick, push up on the bottom of the door, the cables relaxed, then when he took the stick away, the door moved down against the cables, acts like (gravity) is letting the door go down and keeping tension on the cables, imagine that. I think this the best way to understand how this LiftMaster 8500 opener brings the door down.
Just think, if only someone on YouTube could of demonstrated this, this thread would of stopped 6 pages ago, or there would been something a lot more interesting to read.
