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THE
FUNDAMENTALS
Basic
rules
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Higher
tire pressure (within the manufacturer's limits) generally produces
better response and handling, though with a somewhat harsher ride.
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Tire
pressure should always be checked when the tire is cold.
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Heat
contributes to poor performance in tires. Less air pressure means
more tire flex and heat build up. Excessive heat (from overload or
underinflation) can cause sudden tire failure.
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The
lower the pressure, the more likely the tire is to aquaplane
in wet weather.
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Lower
pressure does not improve winter traction -- you want the tire to
bite down to the pavement, not float on the snow.
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Tires
get old and hard with age. Tires with excessive wear can do more
harm than good.
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By
the time tires get down to their wear bars, wet weather traction is
greatly reduced. If possible, replace them sooner, if not adjust
your driving accordingly.
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Narrow
tires are generally better in the rain or snow than wide tires.
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You
get what you pay for. Cheap tires are like a bargain parachute and
may not be up to the task when needed.
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Those
four little patches of rubber, or tire-to-road-surface contact
patches, are all that's keeping your car headed in the chosen
direction. Take care of them. top
Driving
environment
Your car's interior is your
command center while driving. From it you will make every necessary
input to get you and your vehicle from point A to point B. As such, you
should be conscientious about maintaining it in proper working order
just as you would your tires or engine.
Anything loose can either distract you or hurt you. Packages thrown in
the back seat; your dry cleaning hung in a blind spot; sunglasses tossed
carelessly on the dashboard or a mug of hot coffee in your hands can all
serve to make even a benign situation a bad one. In a panic stop or
emergency lane change, all of those unsecured objects will accelerate,
wreaking havoc to your driving environment. Simple physics tell us that
if you were driving at 55 mph and hit the brakes, the car will slow
down, but any thing left unsecured will continue traveling at 55 mph.
That package in the back seat just might accelerate into the back of
your head. top
Driving
position
Every sport has a ready, or
balanced, position that allows the best chance of success. The poise of
a great skier, golfer or tennis player comes from that stance. Whether
it's a racecar or a streetcar, the same basic position applies.
Unless your physique makes this impossible, adjust the seat track so
that, when pressing hard on the brake pedal, you still have a moderate
bend at the knee. Also, try to allow clearance so your knee can move
freely under the steering wheel.
Now adjust the backrest so that when your shoulders are against the seat
back and your arm is resting on the top of the wheel, the wrist joint
reaches the rim. This may not work for everybody in every car, but the
closer you can get to the position the more efficient you are likely to
be in your control inputs.
Buckle up the seat belts and make sure they fit snugly, especially the
lap belt. The left foot should be used to brace, not brake. If your car
has a "dead pedal" or left-foot rest, use it.
Remember that the seat and belt should support you well enough so that
you're not struggling to stay behind the wheel in an emergency lane
change. top
Your
view
Make sure the side view mirrors
perform their intended function. They are meant to view beside the car,
not the side of the car. What do you really need to see; your rear
bumper or the car in the next lane?
Adjust the side mirrors out until you can no longer see the side of your
own car. This should help reduce traditional blind spots. Assuming you
have been scanning the mirrors regularly -- we recommend every three to
seven seconds or so -- a quick shoulder check should be the only
requirement for a safe lane change. top
PERFORMANCE
DRIVING
BRAKING
Rules of braking
There's a lot more to good
emergency braking than knowing which pedal to push. By following a few
basic rules we can optimize stopping ability even in an unfamiliar car.
Rule 1 Cars stop best in a straight line. That's the only time
all the available traction is available for braking.
Rule 2 On virtually every production car there is an initial free
play in the brake pedal that doesn't contribute much to stopping.
The driver needs to quickly reach the hard spot in the pedal when
threshold braking or lock up occurs which can be anywhere from a third
to two-thirds of the way through the total pedal travel.
Rule 3 Threshold or maximum braking occurs when the tires are
turning slightly slower than the vehicle speed. This should generate a
scuffing sound or some squealing of the tires, but not the howling that
occurs when a tire is locked.
Rule 4 Locking up the wheels increases stopping distance by about
twenty-five percent, makes steering impossible, ruins the tires and
scares everybody in the area.
Rule 5 A locked tire can be freed to roll again without going to
the extreme of pumping the brakes. A slight reduction of pressure on the
pedal is all it takes. We refer to this as modulation.
Rule 6 While large leg muscles can get you to the hard spot with
a firm press, more sensitive foot muscles have to deal with pressure
control for the rest of the stop.
Rule 7 Pumping the brakes is outdated, inefficient and upsets the
car's balance.
Rule 8 The faster a car is going, the harder the brakes must be
pressed in order to reach threshold, which we'll call a number 10 pedal
(that would be ten out of ten). To maintain this perfect level, brake
pressure would have to be reduced slightly throughout the stop.
Rule 9 Knee position--shifting the knee towards the left--serves
to line up the joints from hip to ankle and permits more precise use of
the foot muscles.
Rule 10 If a car is being braked with a perfect number 10 pedal
and any steering input is needed, brake pressure must be reduced
accordingly. Otherwise, there would be no traction available for
turning. Anti-lock brakes perform this function electronically, as well
as preventing wheel lock-up in straight line braking.
An analogy we often use in the Dodge/Skip Barber Driving School is to
imagine a string connecting the right foot and the steering wheel. As
the wheel is turning, the string tightens, smoothly pulling the driver's
foot back. If the string unwinds, the driver's foot can press harder on
the pedal. top
The
perfect stop
Let's put this together and create a perfect stop. An incident occurs
and the driver goes quickly to the brake pedal, pressing and squeezing
up to a number 10 pedal. As the car slows and kinetic energy is reduced,
the front wheels start to lock, but the driver curls the right foot back
about a quarter of an inch and the wheels start to turn again. There's a
car blocking the lane ahead and our driver needs to steer, but stopping
is still the goal. As the wheel is turning the foot curls back a bit
more, smoothly balancing grip between the two tasks of turning and
braking. The car stops safely, out of harm's way.
The same incident, with an anti-lock brake equipped car, would be dealt
with in a similar fashion. Once the driver has activated the anti-lock
brakes there's no point second-guessing the system. Keeping the wheels
straight for as long as possible will maximize braking power. When the
wheel is turned, the anti-lock system will perform the balancing act,
keeping the wheels rolling and balancing available traction between the
two tasks. In effect, anti-lock brakes give every driver an educated
foot, something professional drivers spend years practicing and
perfecting. top
Better
anti-lock braking
It's worth noting, though, that anti-lock brakes can fail and also that
it's possible to optimize their performance by understanding the physics
involved. The more cornering force needed, the less traction available
for braking. In some emergency swerves, the driver may need all the
car's traction to make a lane change, so braking would not be possible. top
CORNERING
Hand
versus foot position
In order to be able to drive through corners safely and efficiently we
need to be aware that hand position -- what the driver is doing with the
steering wheel -- and foot position -- which pedal is being depressed
and how much -- are closely linked. top
Power
and steering
In our discussion of load transfer we dealt with the idea that
acceleration generally reduced the traction available for steering. From
this it's possible to reach a simple and elegant conclusion. If we want
to keep our car balanced, we cannot add significant amounts of power
while we're holding or adding steering. If we do, we're contradicting
one input for another, binding up the car. top
The
key to acceleration
When can we accelerate? We can add power at the point where we begin to
reduce the amount of steering as we approach the exit of the corner. It
makes perfect sense. Of course, few drivers are aware of this rule and
in everyday driving it probably isn't that critical, since we're well
below the vehicle's ultimate potential. Remember though that we're
trying to create good habits, and even at slower speeds there is a great
deal of satisfaction to be derived from driving with good timing. top
Avoid
entering too fast
Racing drivers and street drivers share a common goal in negotiation of
a corner; they want to get through the turn and onto the straightaway.
As basic as this sounds, excessive optimism in the form of too high an
approach speed can make this a difficult task.
There are few worse things that can be done with a car than entering a
corner too fast. If speed is truly excessive, the car simply will not
stay on the road. The laws of physics win out and even the world's best
driver can't change that. Therefore the wise approach is "slow
in/fast out" on the track, or more realistically, "slow
in/safe out" as a policy on the street. top
Cornering
techniques
In the Dodge/Skip Barber Driving School, though, we have the opportunity
to work on cornering techniques and explore the car's limit. We learn to
fix the kind of errors that might occur in everyday driving where a
corner turns out to be tighter than it looked, a sudden bump throws the
car off line or perhaps a dog leaps in your path as you round a blind
turn.
A driver's first task is to prepare the car for a turn, and this means
slowing down in a straight line for maximum braking efficiency. This
spot at which the brakes are first applied is called, appropriately, the
braking point.
In a manual gearbox car any downshifts should be done in a straight line
as well. The clutch should never be depressed during a corner. The
brakes may be released before the turn but in most cases trailing the
brake a little into the turn will help keep the car more stable. The
driver is already looking through the turn and in fact has looked before
turning the wheel. In a tight turn this may mean sighting through the
side window.
The purpose is to gain information first, then use it. This is a great
way to avoid surprises. The driver's foot transitions smoothly from the
brake to the accelerator, assuming the view is clear, and then the
accelerator is squeezed smoothly down as the driver dials out the
steering. Note the terminology -- we're not talking about stomps, slam,
kicks or punches. Good driving has it's own vocabulary with words like
trail, feather, modulate and squeeze. top
HANDLING
THE WHEEL
Shuffle
steering
Our preferred method of adding and reducing steering is called shuffle
steering. If you're willing to devote the effort to practice this
technique the result should be more precise steering, more accurate skid
control and a generally calmer driving environment.
Here's how it works. For a left turn, the right hand moves to the bottom
of the steering wheel then pushes the wheel up a full half turn. This
places the right hand at the top of the wheel. Meanwhile, the left hand
has mirrored this movement and slid up to meet the right. The left hand
now pulls the wheel down through another full half turn, while the right
slides down the wheel rim so both hands meet at the bottom. top
The
advantages of shuffle steering
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Both
hands stay on the wheel at all times.
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The
hands never cross over or get jammed on the wheel. (Whatever
technique you've used, try and reposition your hands so they are
close to nine o'clock and three o'clock when cornering.)
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The
driver is able to steer without leaning and losing contact with the
seat back.
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There
is less flailing around of arms than in hand-over-hand so the driver
retains a better sense of where the wheels are pointed. This is
especially significant during skid recovery.
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The
driver retains the stability to feed the wheel back to center after
a turn, rather than letting it slip through the hands. top
The
Don'ts
One of the worst habits we see in traffic is the tendency to steer with
one hand on top of the wheel, the other often resting on the gear lever.
You'd be hard pressed to find a less efficient position, either for
getting good feedback from the car or for control in an emergency. Rest
assured that there is no need to hold on to the shifter, either. The
transmission won't fall out if you let go. Finish the shift then put the
hand back on the wheel where it belongs.
Now that more cars are airbag equipped, this position also means that if
the airbag deploys you'll have a brief and nasty fistfight with yourself
as your arm is thrown backwards.
This is also a good reason to have a hands-free phone if you must use a
cellular phone while driving. Many states are now making it illegal to
drive while holding a phone in part for this reason. Drinking from a
hand mug or smoking a pipe while driving could also be classified as bad
ideas. top
LOAD
TRANSFER
Putting
the traction where you need it
There are three main elements of vehicle dynamics that a driver should
understand. The first of these is load transfer. top
Load
transfer
Let's assume we're starting with a car that's either at rest or balanced
at a steady speed. The load, and therefore the traction, is equally
distributed at the four corners of the vehicle. Any control movement,
even the slightest twitch, will transfer load from one corner to
another. The contact
patch of the unloaded tire will lose traction, while the
loaded tire will gain traction. If we accelerate, the rear tires gain
grip while the front lose grip. Under braking the effect is reversed. top
Power
and traction
A logical conclusion would be that if we are accelerating hard, there
might be less traction available for steering. This is true regardless
of whether the car is front-or rear-wheel drive. It's important to
understand though that this doesn't mean we coast through corners.
Balanced throttle, or steady power, can be useful in many situations.
However, excessive power through a corner is not a good idea. Even if
you get away with it, you'll be developing bad habits. top
Stored
energy
The second key to understanding driving is the principle of stored
energy or spring rebound. Any time a car changes either speed or
direction, springs are either compressed or extended. The return or
rebound of those springs can upset the car's balance, leading to the
dreaded fishtail effect where the car's back end begins to wag
uncontrollably. A good driver will anticipate this phenomenon and be
ready to calm the whole process with careful, well-timed control
applications. top
The
keys to control
Finally, a good driver should recognize that cars have three rudders,
three controls that either alone or together can be used to change
direction. These three rudders are the brake pedal, the throttle pedal
and the steering wheel. top
SLIP,
SLID AND SKID
Slip
Any time a car is cornering, even at fairly sedate speeds, there's some
discrepancy between where the tires are pointed and where the car is
headed. This is just the normal effect of tire scrub. As forces rise,
though, the tires start to slip more relative to the car's direction of
travel.
For example, if the front tires are losing traction due to power understeer,
the tires may be pointed towards the inside of a corner while the car is
plowing towards the outside. The tire's direction represents hope the
car's direction of travel represents reality. The difference between
hope and reality is known as the slip
angle. top
Slide
In high-performance driving, we often use controlled slides, or slip, to
direct the car. As a result, we usually hear a degree of tire noise.
This isn't necessarily a bad thing, it just means the tires are working
fairly close to their limit. top
Skid
When a slide becomes a skid, though, it means we have exceeded the
traction potential of the tire and it is beginning to break away. At
this point the slip
angle will increase dramatically and if the driver responds
quickly the result will be a loss of control. When tire squeal becomes
very loud on dry pavement chances are the limit is near. On wet
pavement, though, there will be little if any tire noise to serve as a
warning and the only squealing may come from the driver or passengers. top
SEASONAL
DRIVING TIPS
Aquaplaning
Avoid aquaplaning by staying out of deep or standing water and by matching speed
to conditions. If your car aquaplanes, stay off the gas or brake, avoid
sudden steering and wait. Nothing else will help. Waiting to regain
traction won't be much fun, but it's all you can do. top
Ice
In truly icy conditions, engine
braking alone may be enough to lock the drive wheels of your car. If
you're in a front drive vehicle you'll lose steering, in a rear drive
the car may begin to spin. If this occurs, put the transmission in
neutral, look, steer, and hope. Once again, the best way to deal with
these situations is to avoid them or anticipate them. The biggest
problem with winter conditions is the unpredictability, so choose a
speed that allows you some traction reserve. top
Snow
driving
The most dangerous road conditions
occur right around freezing temperature. Develop a sense of great
delicacy in control applications. The recovery phase of a skid usually
needs to be done more slowly on snow, since there's less stored energy
in the springs.
While front-wheel drive may give greater traction from a standing start
and four-wheel drive gives a greater sense of stability, the drivetrain
has less to do with the amount of grip available than your tires and
suspension design.
It's easy to feel invulnerable in a four-wheel drive vehicle. But
remember that the laws of physics are irrefutable and no amount of
vehicle technology, including four-wheel drive, will save you when
you've broken them.
When braking in deep snow, without anti-lock brakes, it may help to use
cadence braking -- lock the brakes, releasing only long enough to steer
if the vehicle starts to slide to one side or the other. This is not
just pumping. But long periods of lock up with a short release of brake
pressure when necessary. top
 All
driving tips are provided by Dodge/Skip
Barber Driving School.
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