By Michael Ecord
Driving off-road can be fun and
exciting. Avoid unnecessary
problems by familiarizing yourself with your vehicle and the
characteristics / personality of the machine.
It is important to know the capabilities and limitations of the
4x4. Vehicle clearance,
along with traction and depth limitations effect where and how a trail
will be traversed.
Vehicle Clearance; Become familiar with the low
points on your vehicle and their location in relation to tire position.
Common low points are differentials, spring & shock mounts,
lower control arms, steps, exhaust, & spare tires.
Traction: Both the tires and the 4 wheel
drive system effect traction. Tire
type and air pressure directly relate to traction.
Generally, the more rubber in contact with the trail, the better
the traction. This will be
discussed further under trail types.
Many of the stock four wheel drive systems have limited slip or
open differentials. This
does not allow equal transfer of power to all four tires.
Typically the right rear and left front tire are powered.
Depth Limitations: At some point you will be in
a position to make a water crossing.
It is important to know the height of the air intake for the
engine. Also, the
differentials, transmission, and transfer case have breather ports to
allow the transfer of air during rapid heating and cooling of the unit. Often there is rubber tubing extending the height of the
breathers. The height of
the gas tank fill and vent tube is another location to remember.
Terrain directly effects driving
technique. Hard ground,
sand, and mud all require different styles. Be aware of what is in front
of you. If there is a blind
spot or a difficult section on the trail, stop, get out and check it out
before proceeding. Plan the route (line), taking care to remember about
the low points on the vehicle. Use
a spotter to help guide through the difficult spots.
Also, it is important to remember which tires are powered and try
to keep those on the ground. On
vehicles with solid (live) front axles, disconnecting the front sway bar
can help by increasing the vehicles front-end articulation. Another way
to increase traction on most dry terrains is to air
down. Airing down is
the act of decreasing tire pressure to increase the footprint size of
the tire. A typical rule of thumb is not remove more pressure then
necessary to deflate the tire enough to reduce sidewall height by 25%.
This usually means a tire pressure around 10-15 psi. Do not
decrease pressure below 8 psi. Except in extreme cases.
It takes at least 6 psi. to mount a tire on the rim.
When traveling in groups there are
several additional items to remember. Look out for your fellow
four-wheelers. Do not
follow to close. Allow the vehicle in front to clear an obstacle before
proceeding, e.g. give enough room for the vehicle to back down the hill
to try again. Never loose
sight of the vehicle behind, they may need to be spotted through a
difficult section or aided in recovery.
Rocky terrain: Ground clearance is very important.
Low gears, 1st-3rd are usually preferred.
In dry conditions all terrain tires work very good, placing more tread
on the ground then the same sized, more aggressive, mud terrains.
Large obstacles like steps and ledges can be approached from an
angle, allowing one wheel at a time to mount the obstacle. Brakes should
be used as seldom as possible and then only lightly.
Appling the brakes hard cause the suspension to compress,
reducing clearance. The slower the vehicle crawls over the rocks equals more control that
can be maintained and less risk of damage.
Sand; Don’t do anything suddenly. Try to stay in existing tracks.
Make wide turns and start and stop slowly. This is done to keep
from building a wake of sand in front of the tires. It definitely helps
to air down for driving in the sand.
All terrain tires will tend to rise on top of the sand while mud
terrains will like to dig in. If the vehicle becomes bogged down, try to
back out on your own tracks rather then punching the accelerator.
The later has the tendency to dig you in DEEP.
Hills should always be approached head on.
Never attempt to drive sideways on a slope.
This applies when ascending or descending.
There is a much greater risk to rolling the vehicle on a sideways
approach as compared to the head on approach.
Ascents: Each ascent is different.
Gearing should be selected based on the severity of the slope. If
the ascent is steep, climb the hill in low range. On a hard surface with
ample traction, 1st gear in 4WL should supply all the torque necessary
to clear the ascent. If the
surface is soft or there is a lot of loose gravel, 2nd or 3rd
gear in the low range may be preferred to keep momentum up through the
climb. Caution, to much
momentum can cause loss of control or damage to the vehicle.
Never attempt to turn around on an incline, let the vehicle roll
back down the hill and start again.
Descents: Steep descents should be taken in 1st gear
4WL. Use the engine compression as a brake to slow the vehicle’s
downhill progression. It is better to be in to low of a gear then to
have an out of control vehicle (run away).
To reduce the chance of sliding, resist the temptation to apply
the brakes hard on the descent. If
it is necessary to brake to keep the vehicle from running
away, feather the brakes. Vehicles
with automatic transmissions will have to use their brakes as momentum
increases. If the rear of the vehicle start to slide around on sandy or
muddy slopes try to accelerate through the slide.
Mud: There are many
different types of mud, from the bottomless slop to slimy clay.
Each type requires different technique and equipment.
What ever the type of mud, tires with large lugs are needed so
the tire can clean itself. Otherwise,
the tires become slicks and most of the traction is lost. Aired down
wide tires work best to float over the bottomless goo.
In mud that has a firm substrate, narrow tires that penetrate the
mud offer the best traction. Rocking
the steering wheel back and forth helps the front wheels find traction.
Mud can hide holes and obstacles that will swallow a vehicle or
chew up a tire. Driving in
the mud is very unpredictable
Water Crossings: Be aware
of the vehicles depth limitation. Scout
the water crossing for hidden obstacles and water depth.
Proceed at a slow pace, 2nd gear in four wheel low.
If the water crossing is over bumper height, maintain enough
speed to push a 2”-4” bow wake in front of the vehicle.
If traction is lost during the crossing, slow the vehicle down.
Avoid using the clutch on a standard transmission to keep water from
getting between the flywheel and clutch plate. If the vehicle stalls
because of water entering in through the air intake, do not attempt to
restart the motor until it can be verified that there is no water in the
place recovery gear in an easy to reach spot just in case it is needed.
Ravines / Cracks; When crossing a ravine it is quite common to have two tires without traction. Try to pick a line that will drop the drivers side front tire into the area first. This way pressure is maintained on the driver’s side front and passengers side rear tires, which are the power tires in stock vehicles.