Chamberlain 8550 Manual page 5

2
Tighten the Belt
2.1 2.2
By hand, thread the spring trolley nut on the threaded shaft until it is finger tight against Insert a flathead screwdriver tip into one of the nut ring slots and brace it firmly against the trolley.
the trolley. Do not use any tools.
(To motor unit)
Nut ring
Spring Trolley Nut
slot
2.3
Tighten the spring trolley nut with an adjustable wrench or a 7/16" open end wrench about a quarter turn until the spring releases and snaps the nut ring against the trolley. This sets the spring to
optimum belt tension.
Nut Ring
Nut Ring
BEFORE
AFTER RELEASE
1"
1-1/4"
(2.5 cm)
(3.18 cm)
5