GMC SIERRA 2007 Owner's Manual

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 specic 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.
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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. 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 inated to the
upper limit for cold tires. You’ll nd these numbers
on the Certication label at the rear edge of the
driver’s door or see Loading Your Vehicle 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.
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Weight-Distributing Hitches and Weight
Carrying Hitches
A. Body to Ground Distance
B. Front of Vehiclet
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 use a step-bumper hitch, the bumper could
be damaged in sharp turns. Make sure there is
ample room when turning to avoid contact between
the trailer and the bumper.
If you will be pulling a trailer that, when loaded,
will weigh more than 5,000 lbs (2 270 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 when driving. Always
use a sway control if the trailer will weigh
more than these limits. You can ask a hitch dealer
about sway controls.
Fifth Wheel and Gooseneck Trailering
Fifth wheel and gooseneck trailers can be
used with many pickup models. These trailers
place a larger percentage of the weight (kingpin
weight) on the tow vehicle than conventional
trailers. Make sure this weight does not cause the
vehicle to exceed GAWR or GVWR.
Fifth wheel or gooseneck kingpin weight should be
15 to 25 percent of the trailer weight up to the
maximum amount specied in the trailering chart
for your vehicle. See “Weight of the Trailer” in
this section for more information.
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The hitch should be located in the pickup bed so
that it’s centerline is over or slightly in front of the
rear axle. Take care that it is not so far forward that
it will contact the back of the cab in sharp turns.
This is especially important for short box pickups.
Trailer pin box extensions and sliding fth wheel
hitch assemblies can help this condition. There
should be at least six inches of clearance between
the top of the pickup box and the bottom of the
trailer shelf that extends over the box.
Make sure the hitch is attached to the tow vehicle
frame rails. Do not use the pickup box for support.
Safety Chains
You should always attach chains between your
vehicle and your trailer. Cross the safety chains
under the tongue of the trailer to help prevent the
tongue from contacting the road if it becomes
separated from the hitch. Instructions about safety
chains may be provided by the hitch manufacturer
or by the trailer manufacturer. If you are towing a
trailer up to 5,000 lbs (2 271 kg) with a
factory-installed step bumper, you may attach the
safety chains to the attaching points on the bumper.If you are towing a trailer up to your vehicle’s trailer
rating limit you may attach the safety chains to the
attaching point on the hitch platform. If you are
towing with an aftermarket hitch follow the trailer or
hitch manufacturer’s recommendation for attaching
safety chains. Always leave just enough slack so
you can turn with your rig. Never allow safety
chains to drag on the ground.
Trailer Brakes
If your trailer weighs more than 2,000 lbs (900 kg)
loaded, then it needs its own brakes – and they
must be adequate. Be sure to read and follow the
instructions for the trailer brakes so you’ll be
able to install, adjust and maintain them properly.
If your vehicle is equipped with StabiliTrak
®,
your trailer cannot tap into the vehicle’s hydraulic
brake system.
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Your trailer brake system can tap into the vehicle’s
hydraulic brake system only if:
The trailer parts can withstand 3,000 psi
(20 650 kPa) of pressure.
The trailer’s brake system will use less than
0.02 cubic inch (0.3 cc) of uid from your
vehicle’s master cylinder. Otherwise,
both braking systems won’t work well. You
could even lose your brakes.
If everything checks out this far, make the brake
tap at the port on the master cylinder that
sends the uid to the rear brakes. But don’t use
copper tubing for this. If you do, it will bend
and nally break off. Use steel brake tubing.
Integrated Trailer Brake Control System
Your vehicle may have
an Integrated Trailer
Brake Control (ITBC)
system for electric trailer
brakes.This symbol is located on the Trailer Brake
Control Panel on vehicles with an Integrated
Trailer Brake Control System. The power output to
the trailer brakes is based on the amount of
brake pressure being applied by your vehicle’s
brake system. This available power output to the
trailer brakes can be adjusted to a wide range
of trailering situations.
The ITBC system is integrated with your vehicle’s
brake, anti-lock brake and StabiliTrak
®(if
equipped) systems. In trailering conditions that
cause your vehicle’s anti-lock brake or StabiliTrak
®
systems to activate, power sent to the trailer’s
brakes will be automatically adjusted to minimize
trailer wheel lock-up. This does not imply that
your trailer has the StabiliTrak
®system.
If your vehicle’s brake, anti-lock brake or
StabiliTrak
®systems are not functioning properly,
your ITBC system may not be fully functional
or may not function at all. Make sure all of these
systems are fully operational to ensure full
functionality of the ITBC system.
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The ITBC system is powered through your
vehicle’s electrical system. Turning the ignition off
will also turn off the ITBC system. The ITBC
system is fully functional only when the ignition is
in ON or in RUN.
The ITBC system can only be used with trailers
with electric brakes.
{CAUTION:
Connecting a trailer that is not compatible
with the ITBC system may result in
reduced or complete loss of trailer
braking. There may be an increase in
stopping distance or trailer instability
which could result in personal injury or
CAUTION: (Continued)
CAUTION: (Continued)
damage to your vehicle, trailer, or other
property. An aftermarket controller may be
available for use with trailers with surge,
air or electric-over-hydraulic trailer brake
systems. To determine the type of brakes
on your trailer and the availability of
controllers, check with your trailer
manufacturer or dealer.
When trailering, make sure of the following:
The ITBC system is used only with trailers that
are equipped with electric brakes.
All applicable local and federal laws and
regulations are followed.
All electrical and mechanical connections to
the trailer are made correctly.
The trailer’s brakes are in proper working
condition.
The trailer and vehicle are properly loaded for
the towing condition.
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The ITBC system is a factory installed item.
Out-of-factory installation of this system should not
be attempted. GM is not responsible for warranty
or performance of the system resulting from
out-of-factory installation.
Trailer Brake Control Panel
A. Manual Trailer Brake Apply Lever
B. Trailer Gain Adjustment ButtonsThe ITBC system has a control panel located on
the instrument panel to the left of the steering
column. SeeInstrument Panel Overview
(Base/Uplevel version) on page 206orInstrument
Panel Overview (Premium version) on page 209
for more information on location. The control panel
allows you to adjust the amount of output,
referred to as trailer gain, available to the electric
trailer brakes and allows you to manually apply
the trailer brakes. The Trailer Brake Control Panel
is used along with the Trailer Brake Display
Page on the DIC to adjust and display power
output to the trailer brakes.
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Trailer Brake DIC Display Page
The ITBC system displays messages into the
vehicle’s Driver Information Center (DIC). SeeDIC
Warnings and Messages on page 279for more
information.
The display page indicates Trailer Gain setting,
power output to the electric trailer brakes, trailer
connection and system operational status.
A. Trailer Gain Setting
B. Power Output to Trailer Brakes
C. No trailer with electric brakes connected or fault
presentThe Trailer Brake Display Page can be displayed
by performing any of the following actions:
Scrolling through the DIC menu pages using
the odometer trip stem or the DIC Vehicle
Information button (if equipped).
Pressing a Trailer Gain button – If the Trailer
Brake Display Page is not currently displayed,
pressing a Trailer Gain button will rst
recall the current Trailer Gain setting. After the
Trailer Brake Display Page is displayed,
subsequent depressions of the gain buttons
will then cause the Trailer Gain setting to
change.
Activating the Manual Trailer Brake Apply
lever
Connecting a trailer equipped with electric
trailer brakes
All DIC warning and service messages must rst
be acknowledged by the driver before the
Trailer Brake Display Page can be displayed and
Trailer Gain can be adjusted.
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TRAILER GAIN – This setting is displayed
anytime the Trailer Brake Display Page is active.
This setting can be adjusted from 0.0 to 10.0
with either a trailer connected or disconnected. To
adjust the Trailer Gain, press one of the Trailer
Gain adjustment buttons located on the Trailer
Brake Control Panel. Pressg and hold a gain
button to cause the Trailer Gain to continuously
adjust. To turn the output to the trailer off,
adjust the Trailer Gain setting to 0.0 (zero).
0.0 (zero) gain is the factory default setting. To
properly adjust trailer gain, see the Trailer
Gain Adjustment Procedure later in this section.
TRAILER OUTPUT – This is displayed any time a
trailer with electric brakes is connected. Output
to the electric brakes is based on the amount
of vehicle braking present and relative to
the Trailer Gain setting. Output is displayed from 0
to 10 bars for each gain setting.The Trailer Output will indicate “------“onthe
Trailer Brake Display Page whenever the following
occur:
No trailer is connected.
A trailer without electric brakes is connected
(no DIC message is displayed).
A trailer with electric brakes has become
disconnected (a CHECK TRAILER WIRING
message will also be displayed on the DIC).
There is a fault present in the wiring to
the electric trailer brakes (a CHECK TRAILER
WIRING message will also be displayed on
the DIC).
There is a fault in the ITBC system (a
SERVICE TRAILER BRAKE SYSTEM
message will also be displayed in the DIC).
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Manual Trailer Brake Apply
The Manual Trailer Brake Apply Lever is located on
the Trailer Brake Control Panel and is used to apply
the trailer’s electric brakes independent of your
vehicle’s brakes. This lever is used in the Trailer
Gain Adjustment Procedure to properly adjust the
power output to the trailer brakes. Sliding the lever
to the left will apply only the trailer brakes. The
power output to the trailer is indicated in the Trailer
Brake Display Page in the DIC. If your vehicle’s
service brakes are applied while using the Manual
Trailer Brake Apply Lever, the trailer output power
will be the greater of the two.
The trailer and the vehicle’s brake lamps will come
on when either vehicle braking or manual trailer
brakes are applied.
Trailer Gain Adjustment Procedure
Trailer Gain should be set for a specic trailering
condition and must be adjusted any time
vehicle loading, trailer loading or road surface
conditions change.
Setting the Trailer Gain properly is needed for the
best trailer stopping performance. A trailer that
is over-gained may result in locked trailer brakes.
A trailer that is under-gained may result in notenough trailer braking. Both of these conditions
may result in poorer stopping and stability of
the vehicle and trailer.
Use the following procedure to correctly adjust
Trailer Gain for each towing condition:
1. Make sure the trailer brakes are in proper
working condition.
2. Connect a properly loaded trailer to the
vehicle and make all necessary mechanical
and electrical connections. SeeLoading Your
Vehicle on page 425for more information.
3. After the electrical connection is made to a
trailer equipped with electric brakes:
A TRAILER CONNECTED message will be
briey displayed on the DIC display.
The Trailer Brake Display Page will appear
on the DIC showing TRAILER GAIN and
TRAILER OUTPUT.
In the Trailer Output display on the
DIC, “------“will disappear if there is no
error present. Connecting a trailer without
electric brakes will not clear the six dashed
lines.
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