Hummer 2007 H3 - Manual (Page 302)

Consider the following example:
A vehicle model base weight is 5,500 lbs
(2 495 kg); 2,800 lbs (1 270 kg) at the front
axle and 2,700 lbs (1 225 kg) at the rear axle.
It has a GVWR of 7,200 lbs (3 266 kg), a
RGAWR of 4,000 lbs (1 814 kg) and a GCWR
(Gross Combination Weight Rating) of 14,000 lbs
(6 350 kg). The trailer rating should be:
You can expect tongue weight to be at least
10 percent of trailer weight (850 lbs (386 kg)) and
because the weight is applied well behind the
rear axle, the effect on the rear axle will be greater
than just the weight itself, as much as 1.5 times
as much. The weight at the rear axle could
be 850 lbs (386 kg) X 1.5 = 1,275 lbs (578 kg).
Since the rear axle already weighs 2,700 lbs
(1 225 kg), adding 1,275 lbs (578 kg) brings the
total to 3,975 lbs (1 803 kg). This is very close to,
but within the limit for RGAWR as well. The
vehicle is set to trailer up to 8,500 lbs (3 856 kg).
But let’s say your specific vehicle is equipped with
some of the latest options and you have a front
seat passenger and two rear seat passengers with
some luggage and gear in the vehicle as well.
You may add 300 lbs (136 kg) to the front
axle weight and 400 lbs (181 kg) to the rear axle
weight. Your vehicle now weighs:
Weight is still below 7,200 lbs (3 266 kg) and you
may think that you should subtract 700 additional
pounds (318 kg) from your trailering capacity
to stay within GCWR limits. Your maximum
trailer would only be 7,800 lbs (3 538 kg).
You may go further and think you must limit
tongue weight to less than 1,000 lbs (454 kg)
to avoid exceeding GVWR. But, you must
still consider the effect on the rear axle.
Because your rear axle now weighs 3,100 lbs
(1 406 kg), you can only put 900 lbs (408 kg)
on the rear axle without exceeding RGAWR.
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