GMC 2011 Sierra Owner's Manual page 328

When the truck camper is
loaded, drive to a scale and
weigh on the front and on the
rear wheels separately to
determine axle loads. Individual
axle loads should not exceed
either of the gross axle weight
ratings (GAWR). The total axle
loads should not exceed your
vehicle's gross vehicle weight
rating (GVWR). These ratings
are given on the vehicle
certification label attached to
the rear edge of the driver door.
See Certification/Tire Label
under
. If weight ratings
are exceeded, move or remove
items to bring all weights below
the ratings.
See your dealer for more
information on curb weights,
cargo weights, Cargo Weight
Rating and the correct center
of gravity zone.