Brakes GMC SONOMA 1999 User Guide

4-8
Here's how anti-lock works. Let's say the road is wet.
You're driving safely. Suddenly an animal jumps out in
front of you.
You slam on the brakes. Here's what happens with ABS.
A computer senses that wheels are slowing down. If one
of the wheels is about to stop rolling, the computer will
separately work the brakes at each front wheel and at
both rear wheels.The anti
-lock system can change the brake pressure faster
than any driver could. The computer is programmed to
make the most of available tire and road conditions.
You can steer around the obstacle while braking hard.
As you brake, your computer keeps receiving updates on
wheel speed and controls braking pressure accordingly.

4-9
Remember: Anti-lock doesn't change the time you need
to get your foot up to the brake pedal or always decrease
stopping distance. If you get too close to the vehicle in
front of you, you won't have time to apply your brakes
if that vehicle suddenly slows or stops. Always leave
enough room up ahead to stop, even though you have
anti
-lock brakes.
Using Anti
-Lock
Don't pump the brakes. Just hold the brake pedal down
firmly and let anti
-lock work for you. You may feel the
brakes vibrate, or you may notice some noise, but this is
normal. On vehicles with four
-wheel drive, your
anti
-lock brakes work at all times -- whether you
are in two
-wheel drive or four-wheel drive.
Braking in Emergencies
With anti-lock, you can steer and brake at the same
time. In many emergencies, steering can help you more
than even the very best braking.
Steering
Power Steering
If you lose power steering assist because the engine
stops or the system is not functioning, you can steer but
it will take much more effort.
Steering Tips
Driving on Curves
It's important to take curves at a reasonable speed.
A lot of the ªdriver lost controlº accidents mentioned on
the news happen on curves. Here's why:
Experienced driver or beginner, each of us is subject to
the same laws of physics when driving on curves. The
traction of the tires against the road surface makes it
possible for the vehicle to change its path when you turn
the front wheels. If there's no traction, inertia will keep
the vehicle going in the same direction. If you've ever
tried to steer a vehicle on wet ice, you'll understand this.
The traction you can get in a curve depends on the
condition of your tires and the road surface, the angle at
which the curve is banked, and your speed. While you're
in a curve, speed is the one factor you can control.
Suppose you're steering through a sharp curve. Then you
suddenly accelerate. Both control systems
-- steering and
acceleration
-- have to do their work where the tires meet
the road. Adding the sudden acceleration can demand too
much of those places. You can lose control.
What should you do if this ever happens? Ease up on the
accelerator pedal, steer the vehicle the way you want it
to go, and slow down.

4-10
Speed limit signs near curves warn that you should
adjust your speed. Of course, the posted speeds are
based on good weather and road conditions. Under less
favorable conditions you'll want to go slower.
If you need to reduce your speed as you approach a
curve, do it before you enter the curve, while your front
wheels are straight ahead.
Try to adjust your speed so you can ªdriveº through the
curve. Maintain a reasonable, steady speed. Wait to
accelerate until you are out of the curve, and then
accelerate gently into the straightaway.
Steering in Emergencies
There are times when steering can be more effective than
braking. For example, you come over a hill and find a
truck stopped in your lane, or a car suddenly pulls out
from nowhere, or a child darts out from between parked
cars and stops right in front of you. You can avoid these
problems by braking
-- if you can stop in time. But
sometimes you can't; there isn't room. That's the time for
evasive action
-- steering around the problem.
Your vehicle can perform very well in emergencies like
these. First apply your brakes. (See ªBraking in
Emergenciesº earlier in this section.) It is better to
remove as much speed as you can from a possible
collision. Then steer around the problem, to the left or
right depending on the space available.
An emergency like this requires close attention and a
quick decision. If you are holding the steering wheel at
the recommended 9 and 3 o'clock positions, you can
turn it a full 180 degrees very quickly without removing
either hand. But you have to act fast, steer quickly, and
just as quickly straighten the wheel once you have
avoided the object.
The fact that such emergency situations are always
possible is a good reason to practice defensive driving at
all times and wear safety belts properly.

4-13
Loss of Control
Let's review what driving experts say about what
happens when the three control systems (brakes, steering
and acceleration) don't have enough friction where the
tires meet the road to do what the driver has asked.
In any emergency, don't give up. Keep trying to steer and
constantly seek an escape route or area of less danger.
Skidding
In a skid, a driver can lose control of the vehicle.
Defensive drivers avoid most skids by taking reasonable
care suited to existing conditions, and by not ªoverdrivingº
those conditions. But skids are always possible.
The three types of skids correspond to your vehicle's
three control systems. In the braking skid, your wheels
aren't rolling. In the steering or cornering skid, too
much speed or steering in a curve causes tires to slip and
lose cornering force. And in the acceleration skid, too
much throttle causes the driving wheels to spin.
A cornering skid and an acceleration skid are best
handled by easing your foot off the accelerator pedal.If your vehicle starts to slide, ease your foot off the
accelerator pedal and quickly steer the way you want the
vehicle to go. If you start steering quickly enough, your
vehicle may straighten out. Always be ready for a
second skid if it occurs.
Of course, traction is reduced when water, snow, ice,
gravel or other material is on the road. For safety, you'll
want to slow down and adjust your driving to these
conditions. It is important to slow down on slippery
surfaces because stopping distance will be longer and
vehicle control more limited.
While driving on a surface with reduced traction, try
your best to avoid sudden steering, acceleration or
braking (including engine braking by shifting to a lower
gear). Any sudden changes could cause the tires to slide.
You may not realize the surface is slippery until your
vehicle is skidding. Learn to recognize warning
clues
-- such as enough water, ice or packed snow on
the road to make a ªmirrored surfaceº
-- and slow down
when you have any doubt.
Remember: Any anti
-lock brake system (ABS) helps
avoid only the braking skid.

4-14
Off-Road Driving with Your
Four
-Wheel-Drive Vehicle
This off-road guide is for vehicles that have
four
-wheel drive.
Also, see ªAnti
-Lock Brakesº in the Index.
If your vehicle doesn't have four
-wheel drive, you shouldn't
drive off
-road unless you're on a level, solid surface.
Off
-road driving can be great fun. But it does have some
definite hazards. The greatest of these is the terrain itself.
ªOff
-roadingº means you've left the great North
American road system behind. Traffic lanes aren't
marked. Curves aren't banked. There are no road signs.
Surfaces can be slippery, rough, uphill or downhill.
In short, you've gone right back to nature.
Off
-road driving involves some new skills. And that's
why it's very important that you read this guide. You'll
find many driving tips and suggestions. These will help
make your off
-road driving safer and more enjoyable.
Before You Go Off-Roading
There are some things to do before you go out. For
example, be sure to have all necessary maintenance and
service work done. Check to make sure all underbody
shields (if so equipped) are properly attached.
Be sure you read all the information about your
four
-wheel-drive vehicle in this manual. Is there enough
fuel? Is the spare tire fully inflated? Are the fluid levels
up where they should be? What are the local laws that
apply to off
-roading where you'll be driving? If you
don't know, you should check with law enforcement
people in the area. Will you be on someone's private
land? If so, be sure to get the necessary permission.
Loading Your Vehicle for Off-Road Driving
There are some important things to remember about
how to load your vehicle.

The heaviest things should be on the load floor and
forward of your rear axle. Put heavier items as far
forward as you can.

Be sure the load is secured properly, so driving on
the off
-road terrain doesn't toss things around.

4-21 Driving Downhill
When off-roading takes you downhill, you'll want to
consider a number of things:

How steep is the downhill? Will I be able to maintain
vehicle control?

What's the surface like? Smooth? Rough? Slippery?
Hard
-packed dirt? Gravel?

Are there hidden surface obstacles? Ruts?
Logs? Boulders?

What's at the bottom of the hill? Is there a hidden
creek bank or even a river bottom with large rocks?
If you decide you can go down a hill safely, then try to
keep your vehicle headed straight down, and use a low
gear. This way, engine drag can help your brakes and
they won't have to do all the work. Descend slowly,
keeping your vehicle under control at all times.
CAUTION:
Heavy braking when going down a hill can cause
your brakes to overheat and fade. This could
cause loss of control and a serious accident.
Apply the brakes lightly when descending
a hill and use a low gear to keep vehicle speed
under control.
Q:Are there some things I should not do when
driving down a hill?
A:Yes! These are important because if you ignore them
you could lose control and have a serious accident.

When driving downhill, avoid turns that take you
across the incline of the hill. A hill that's not too
steep to drive down may be too steep to drive across.
You could roll over if you don't drive straight down.

Never go downhill with the transmission in
NEUTRAL (N), or with the clutch pedal depressed
in a manual shift. This is called ªfree
-wheeling.º
Your brakes will have to do all the work and could
overheat and fade.

4-22
Q:Am I likely to stall when going downhill?
A:It's much more likely to happen going uphill.
But if it happens going downhill, here's what to do.

Stop your vehicle by applying the regular brakes.
Apply the parking brake.

Shift to PARK (P) (or to NEUTRAL (N) with the
manual transmission) and, while still braking, restart
the engine.

Shift back to a low gear, release the parking brake,
and drive straight down.

If the engine won't start, get out and get help.
Driving Across an Incline
Sooner or later, an off-road trail will probably go across
the incline of a hill. If this happens, you have to decide
whether to try to drive across the incline. Here are some
things to consider:

A hill that can be driven straight up or down may be
too steep to drive across. When you go straight
up or down a hill, the length of the wheel base
(the distance from the front wheels to the rear
wheels) reduces the likelihood the vehicle will
tumble end over end. But when you drive across
an incline, the much more narrow track width
(the distance between the left and right wheels) may
not prevent the vehicle from tilting and rolling over.
Also, driving across an incline puts more weight on
the downhill wheels. This could cause a downhill
slide or a rollover.

4-25
Hard packed snow and ice offer the worst tire traction. On
these surfaces, it's very easy to lose control. On wet ice, for
example, the traction is so poor that you will have difficulty
accelerating. And if you do get moving, poor steering and
difficult braking can cause you to slide out of control.
CAUTION:
Driving on frozen lakes, ponds or rivers can be
dangerous. Underwater springs, currents under
the ice, or sudden thaws can weaken the ice. Your
vehicle could fall through the ice and you and
your passengers could drown. Drive your vehicle
on safe surfaces only.
Driving in Water
Light rain causes no special off-road driving problems.
But heavy rain can mean flash flooding, and flood
waters demand extreme caution.
Find out how deep the water is before you drive through
it. If it's deep enough to cover your wheel hubs, axles or
exhaust pipe, don't try it
-- you probably won't get
through. Also, water that deep can damage your axle
and other vehicle parts.If the water isn't too deep, then drive through it slowly.
At fast speeds, water splashes on your ignition system and
your vehicle can stall. Stalling can also occur if you get
your tailpipe under water. And, as long as your tailpipe is
under water, you'll never be able to start your engine.
When you go through water, remember that when your
brakes get wet, it may take you longer to stop.
CAUTION:
Driving through rushing water can be dangerous.
Deep water can sweep your vehicle downstream
and you and your passengers could drown. If it's
only shallow water, it can still wash away the
ground from under your tires, and you could lose
traction and roll the vehicle over. Don't drive
through rushing water.
See ªDriving Through Waterº in the Index for more
information on driving through water.

4-29
Driving too fast through large water puddles or even
going through some car washes can cause problems, too.
The water may affect your brakes. Try to avoid puddles.
But if you can't, try to slow down before you hit them.
CAUTION:
Wet brakes can cause accidents. They won't work
as well in a quick stop and may cause pulling to
one side. You could lose control of the vehicle.
After driving through a large puddle of water or
a car wash, apply your brake pedal lightly until
your brakes work normally.
Hydroplaning
Hydroplaning is dangerous. So much water can build up
under your tires that they can actually ride on the water.
This can happen if the road is wet enough and you're
going fast enough. When your vehicle is hydroplaning,
it has little or no contact with the road.
Hydroplaning doesn't happen often. But it can if your
tires do not have much tread or if the pressure in one or
more is low. It can happen if a lot of water is standing on
the road. If you can see reflections from trees, telephone
poles or other vehicles, and raindrops ªdimpleº the
water's surface, there could be hydroplaning.

4-35

Keep your vehicle in good shape. Check all fluid
levels and also the brakes, tires, cooling system and
transmission. These parts can work hard on
mountain roads.

Know how to go down hills. The most important
thing to know is this: let your engine do some of the
slowing down. Shift to a lower gear when you go
down a steep or long hill.
CAUTION:
If you don't shift down, your brakes could
get so hot that they wouldn't work well. You
would then have poor braking or even none going
down a hill. You could crash. Shift down to let
your engine assist your brakes on a steep
downhill slope.
CAUTION:
Coasting downhill in NEUTRAL (N) or with the
ignition off is dangerous. Your brakes will have to
do all the work of slowing down. They could get so
hot that they wouldn't work well. You would then
have poor braking or even none going down a hill.
You could crash. Always have your engine running
and your vehicle in gear when you go downhill.

Know how to go uphill. You may want to shift down
to a lower gear. The lower gears help cool your engine
and transmission, and you can climb the hill better.

Stay in your own lane when driving on two
-lane
roads in hills or mountains. Don't swing wide or cut
across the center of the road. Drive at speeds that let
you stay in your own lane.

As you go over the top of a hill, be alert. There could be
something in your lane, like a stalled car or an accident.

You may see highway signs on mountains that warn of
special problems. Examples are long grades, passing or
no
-passing zones, a falling rocks area or winding
roads. Be alert to these and take appropriate action.