Saab 9-7x Owner's Manual page 249

The effect of tongue weight is about 1.5 times the actual
weight. Dividing the 900 lbs (408 kg) by 1.5 leaves you
with being able to handle only 600 lbs (272 kg) of tongue
weight. Since tongue weight is usually at least 10 percent
of total loaded trailer weight, you can expect that the
largest trailer your vehicle can properly handle is
6,000 lbs (2 721 kg).
It is important that you make sure your vehicle does
not exceed any of its ratings — GCWR, GVWR,
RGAWR, Maximum Trailer Rating or Tongue Weight.
The only way to be sure you are not exceeding any
of these ratings is to weigh your vehicle and trailer.
Total Weight on Your Vehicle's Tires
Be sure your vehicle's tires are inflated to the upper
limit for cold tires. You'll find these numbers on
the Certification label at the rear edge of the driver's
door or see Loading Your Vehicle on page 4-22 for
more information. Then be sure you don't go over the
GVW limit for your vehicle, or the GAWR, including
the weight of the trailer tongue. If you use a weight
distributing hitch, make sure you don't go over the
rear axle limit before you apply the weight distribution
spring bars.
Hitches
It's important to have the correct hitch equipment.
Crosswinds, large trucks going by and rough roads
are a few reasons why you'll need the right hitch.
Weight Distributing Hitches and Weight
Carrying Hitches
(A) Body to Ground Distance, (B) Front of Vehicle
When using a weight-distributing hitch, the hitch must
be adjusted so the distance (A) remains the same both
before and after coupling the trailer to the tow vehicle.
If you will be pulling a trailer that, when loaded, will
weigh more than 4,000 lbs (1 814 kg) be sure to use a
properly mounted weight-distributing hitch and sway
control of the proper size. This equipment is very
important for proper vehicle loading and good handling
4-35