GMC 2007 Sierra - Manual (Page 419)

For example, adding a 700 lb (318 kg) snow plow
actually adds more than 700 lbs (318 kg) to the
front axle. Using the formula, if the snow plow
is 4 ft (122 cm) in front of the front axle and the
wheel base is 10 ft (305 cm), then:
W = 700 lb (318 kg)
A = 4 ft (122 cm)
W.B. = 10 ft (305 cm)
(W x (A + W.B.))/W.B. = (700 x (4 + 10))/10 =
980 lbs (445 kg)
So, if your truck’s front axle reserve capacity is
more than 980 lbs (445 kg), you could add
the snow plow without exceeding the front GAWR.
Q:
What if I want to add heavier equipment
to my vehicle?
A:
You can add heavier equipment on the front
of the vehicle if you compensate for it by
carrying fewer passengers, less cargo, or by
positioning cargo towards the rear. This
has the effect of reducing the load on the front.
However, the front GAWR, rear GAWR, and
the Gross Vehicle Weight Rating (GVWR)
must never be exceeded.
{ CAUTION:
On some vehicles that have certain front
mounted equipment, such as a snow
plow, it may be possible to load the front
axle to the front gross axle weight rating
(GAWR) but not have enough weight on
the rear axle to have proper braking
performance. If your brakes can not work
properly, you could have a crash. To help
your brakes work properly when a snow
plow is installed, always follow the snow
plow manufacturer or installer’s
recommendation for rear ballast to ensure
a proper front and rear weight distribution
ratio, even though the actual front weight
may be less than the front GAWR, and the
total vehicle weight is less than the gross
vehicle weight rating (GVWR). Maintaining
a proper front and rear weight distribution
ratio is necessary to provide proper
braking performance.
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