FORD 2011 F-550 v.4 - Manual (Page 252)

WARNING: The hitch rating listed on the trailer hitch label are
maximum possible trailer ratings for that hitch but may not be
what your vehicle is capable of towing. To find the maximum trailer
weight allowed for your specific vehicle, consult your authorized dealer
(or the RV and Trailer Towing Guide provided by your authorized
dealer).
WARNING: Towing trailers beyond the maximum tongue weight
exceeds the limit of the towing system and could result in
vehicle structural damage, loss of vehicle control and personal injury.
Weight-distributing hitch
When hooking-up a trailer using a weight-distributing hitch, always use
the following procedure:
1. Park the vehicle (without the trailer) on a level surface.
2. Measure the height of the top of the front wheel opening on the
fender, this is H1.
3. Attach the trailer to the vehicle without the weight distributing bars
connected.
4. Measure the height of the top of the front wheel opening on the
fender a second time, this is H2.
5. Install and adjust the tension in the weight distributing bars so that
the height of the front fender is approximately halfway between H1 and
H2.
6. Check that the trailer is level. If not level, adjust the ball height
accordingly and repeat Steps 3–6.
WARNING: Do not adjust a weight-distributing hitch to any
position where the rear bumper of the vehicle is higher than it
was before attaching the trailer. Doing so will defeat the function of
the weight-distributing hitch, which may cause unpredictable handling,
and could result in serious personal injury.
Fifth-wheel trailer hitch (if equipped)
To find the maximum trailer weight allowed for your vehicle, consult
your authorized dealer (or the RV and Trailer Towing Guide provided
by your authorized dealer).
Tires, Wheels and Loading
252
2011 F-250/350/450/550 (f23)
Owners Guide, 4th Printing
USA (fus)