Buick 2005 Century - Manual (Page 206)

Weight of the Trailer Tongue
The tongue load (A) of any trailer is an important weight
to measure because it affects the total or gross weight
of the vehicle. The Gross Vehicle Weight (GVW)
includes the curb weight of the vehicle, any cargo in it,
and the people who will be riding in the vehicle.
If there are a lot of options, equipment, passengers or
cargo in the vehicle, it will reduce the tongue weight the
vehicle can carry, which will also reduce the trailer
weight the vehicle can tow. And if you tow a trailer, you
must add the tongue load to the GVW because the
vehicle will be carrying that weight, too. See Loading
Your Vehicle on page 4-31 for more information
about the vehicle’s maximum load capacity.
When using a weight-carrying hitch, the trailer
tongue (A) should weigh 10 percent to 15 percent of
the total loaded trailer weight (B).
After the trailer is loaded, weigh the trailer and the
tongue, separately, to see if the weights are proper.
The correct weight could be achieved simply by moving
some items around in the trailer.
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