GMC Sierra 2015 Owner's Manual page 287

9-20 Driving and Operating
When using this upper load
platform, be sure the load is
securely tied down to prevent it
from shifting. The load's center
of gravity should be positioned
in a zone over the rear axle. The
zone is located in the area
between the front of each wheel
well and the rear of each wheel
well. The center of gravity height
must not extend above the top
of the pickup box flareboard.
Any load that extends beyond
the vehicle's taillamp area must
be properly marked according to
local laws and regulations.
Remember not to exceed the
Gross Axle Weight
Rating (GAWR) of the front or
rear axle.
Add-On Equipment
When carrying removable items,
a limit on how many people
carried inside the vehicle may
be necessary. Be sure to weigh
the vehicle before buying and
installing the new equipment.
Caution
Overloading the vehicle may
cause damage. Repairs would not
be covered by the vehicle
warranty. Do not overload the
vehicle.
Remember not to exceed the
Gross Axle Weight
Rating (GAWR) of the front or
rear axle.
Maximum
* Equipment Weight
Ladder Rack 340 kg (750 lb)
and Cargo
Cross Toolbox 181 kg (400 lb)
and Cargo
Side Boxes 113 kg per
and Cargo side (250 lb
per side)
* The combined weight for all
rail-mounted equipment should
not exceed 454 kg (1,000 lb).