2002 Ford Explorer
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Ford Explorer Page
| DRIVING DYNAMICS
"The dynamics targets for the new Explorer were clear: Make
it ride and handle better than ever before, including being more
stable, safer, easier to drive and more reassuring. In order to
achieve that, we had to start over and design the first purpose-built
chassis for a Ford SUV - an all-new Explorer from the tires to the
roof-rack."
The 2002 Ford Explorer's new independent rear suspension is literally
at the base of the vehicle's most significant innovations - including
its improved ride, handling and package.
Added to this are a stiffer frame, more precise steering, new front
suspension, improved powertrains and several chassis detail changes
- all of which work to fulfill Explorer's promise of offering a
significantly smoother and more pleasant driving experience.
The dynamics team focused on four key attributes related to the
driving experience: agility, precision, stability and comfort. The
objective was to create the ideal balance between the four without
making compromises. Independent Rear Suspension Explorer's new independent rear suspension (IRS) system replaces
the former solid axle design. IRS offers significantly better handling
over both smooth and rough surfaces. Working with the new front
suspension, IRS reduces rear-end squat during acceleration and front
dive/rear jacking during emergency braking.
IRS offers ride and handling benefits over a solid rear axle design
because each wheel reacts independently to bumps in the road, moving
both up and rearward to absorb the bumps and reduce impact harshness.
The result is improved ride quality.
Because each component performs very specific tasks, the suspension
can be designed to be extremely stiff laterally, while offering
more longitudinal compliance.
These two important functions are more easily separated than in
traditional solid-axle designs, which typically offer high longitudinal
stiffness - because the axles are bolted to long leaf springs and,
thus, offer imprecise lateral control.
The IRS's ability to soak up longitudinal forces, such as those
imposed by potholes or sharp pavement bumps, translates directly
into a more comfortable ride and reduced harshness. Maintaining
lateral stiffness helps keep the rear of the vehicle from swaying
side-to-side in bumps or maneuvers. Likewise, it reduces sensitivity
to wind gusts. In addition, the suspension's ability to maintain
optimum contact between the tires and pavement also helps communicate
important feedback - handling "feel" - to the driver through the
steering wheel.
In highway dips, Explorer's suspension is designed to deliver a
ride that's plush without wallowing. In abrupt, high-speed lane
changes, Explorer is designed to respond quickly to steering and
track predictably.
Explorer's new IRS configuration also is designed to drastically
reduce rear-end skate, which is the lateral movement that occurs
when a vehicle with a solid rear axle travels over sharp bumps or
washboard/corrugated road surfaces.
The new suspension has a short- and long-arm (SLA) and coil-over-shock
design. The upper control arm is cast aluminum. The lower control
arm is stamped steel.
The IRS configuration permits the rear floor of the vehicle to
be lowered nearly 7 inches. This lower floor allows the new Explorer
to offer an optional third-row seat with plenty of headroom and
without compromising cargo space or utility. Even with the lower
floor, overall ground clearance was able to be improved an inch
- which strengthens the vehicle's off-road capabilities.
This innovative packaging of the new IRS system is achieved through
the "porthole-in-frame" design technique. The design is related
to the way the rear half-shafts are packaged - literally via holes
in the frame versus under the frame.
A traditional truck or SUV frame is straight from front to back,
with ladder-like braces across it for strength. The line cannot
be completely straight, however, because it would run into the rear
axle assembly.
That is why nearly every manufacturer puts a large semi-circular
bend in the frame to follow the rear wheel well. The rear axle then
runs beneath it, which limits interior space. For Explorer, using
the traditional wisdom would have meant a narrow third-row seat.
To overcome these obstacles, the Explorer team members had to think
differently.
"After a brainstorming session one day, we asked ourselves why
we were trying to work around the frame. Instead, we decided to
put a porthole in it and work with it," explains Manfred Rumpel,
chassis integration manager. "We worked out some calculations in
basic frame theory and physics, and we were able to prove that a
porthole-in-frame design would have all the necessary strength and
much better packaging flexibility."
The circular hole on each side of the rear frame is reinforced
with a steel tubular tunnel that provides exceptional strength and
room for the half-shafts to move.
Rumpel and other team members have applied for five patents on
Explorer, including the "porthole-in-frame" design.
Other rear changes include the shock damping, which has been increased
to reduce suspension bounce and make the vehicle feel more firmly
planted on the ground when traversing rough surfaces and undulating
roads.
A new hollow rear stabilizer bar is used. It is nearly 40-percent
lighter than the previous solid bar but provides comparable performance.
Urethane bushings - used previously in front stabilizer bars only
- are now used in the rear. The change further helps to isolate
the driver from road noise. Front suspension Explorer's front suspension also is a short- and long-arm (SLA)
design with significant revisions such as a shorter front-end overhang
that result in a tighter turning circle (36.7 feet versus the previous
38.4 feet), crisper steering, improved response to sharp bumps,
better cornering capabilities and enhanced durability.
The front suspension also uses a coil-over-shock design, replacing
the previous torsion bar arrangement. Switching from torsion bars
to coil springs reduces rough-road steering column shake and ride
harshness by allowing suspension components to better absorb fore-aft
impact forces when a wheel hits a sharp bump. Coil springs also
maintain vehicle ride height better than torsion bars - thus reducing
the potential for front-end realignment in older vehicles.
Shock damping has been increased, as in the rear. Also changed
are all-new upper and lower control arms, bushings, and stabilizer
links and retainers. The stabilizer bar is held in position with
urethane bushings that offer better on-center steering than traditional
rubber bushings.
Also improved is the "scrub radius" - the distance between the
tire centerline and the point at which an imaginary line between
the upper and lower ball joints intersects with the ground. It has
been reduced from 2.5 inches to 0.5 inches. Minimizing the scrub
radius improves tire wear and straight-line tracking by reducing
pull when front braking is uneven.
Driver feedback also benefits from a considerable attention to
detail. Explorer's brake pedal is designed to be firm and progressive,
allowing the driver to modulate braking force by feel. Acceleration
is strong at tip-in, without excessive whine and roar. The throttle-cable
was tuned to damp vibrations that could travel via the cable through
the accelerator pedal and to the driver's foot. The engine is designed
to sound reassuringly healthy under full-throttle runs, but disappear
into the background at normal speeds. AdvanceTracTM Interactive vehicle dynamics Explorer will be available with AdvanceTrac™- a computer-driven
interactive vehicle dynamics system - early in 2002. It is Ford's
first SUV available with such technology. The system enhances stability
in extreme driving conditions when drivers misjudge speed or road
conditions.
Developed in conjunction with Ford's involvement with Formula One
racing, the optional AdvanceTrac™ system monitors driver inputs,
such as steering, throttle and brakes, and the corresponding vehicle
response - yaw, lateral acceleration and wheel speed - to control
brake force distribution and vehicle stability.
AdvanceTracTM helps maintain vehicle stability at the
limits of tire adhesion via a combination of yaw rate sensors, the
antilock braking system and traction control system.
Data from the yaw rate sensor, a steering-wheel position sensor,
a lateral acceleration sensor and wheel speed sensors are monitored
through the ABS control module.
When required, AdvanceTracTM applies the brakes at one
or more wheels to correct excessive yaw. If the vehicle's yaw rate
is excessive in a turn, brake force on the outside front wheel helps
keep the vehicle on the desired path. If the yaw rate is lower than
that intended by the driver, force is applied to the inside front
brake.
Explorer's antilock braking system with electronic brake force
distribution will be offered from introduction. The fully integrated
AdvanceTracTM system will be introduced early 2002.
Improved Control TracTM 4x4 Performance Explorer's optional Control TracTM four-wheel-drive system has
been refined for 2002 to make it more "transparent" to the driver,
while improving its abilities in limited traction situations. (For
details, see Powertrain/Drivetrain section.) Steering All Explorer models are equipped with power rack-and-pinion steering,
in addition to the steering improvements provided by the revised
front suspension geometry - including a 1.7-foot tighter turning
radius. The system has a modified steering linkage that results
in a more precise feel.
A tilt/rake steering column is standard on XLS and XLT models.
A combination tilt/telescoping, rake/reach column is standard on
Eddie Bauer and Limited models. The steering column tilts over an
arc range of 2.8 inches and telescopes over a range of 1.8 inches.
The steering wheel itself also has been redesigned to improve its
feel across a broader range of hand sizes. Key changes include re-profiled
detents on the backside of the wheel.
Brakes Explorer's four-wheel disc brakes have been improved for quieter
operation and more responsive pedal effort and consistency.
Explorer's four-wheel, three-channel antilock braking system (ABS)
with electronic brake force distribution (EBD) is standard. The
ABS controls the front wheels independently and the rear wheels
in tandem during heavy braking - to improve vehicle control.
The ABS with EBD employs dynamic proportioning to achieve shorter
stopping distances. It works by measuring braking force versus traction
and allocating brake force to the wheels that have the best grip
for stopping even before the ABS system kicks in. This helps reduce
the braking distance.
The front discs have: larger rotors (305 millimeters compared with
286 mm) for reduced operating temperatures; new low-metallic-content,
non-asbestos lining for reduced noise; stiffer calipers with added
lining volume and swept area to provide more uniform brake pad loading
for reduced noise and wear; and an optimized brake pad insulator
for reduced brake noise.
The rear discs increase from 11.2 inches to 11.8 inches (285 mm
to 301 mm).
Tires Explorer is available in a wide variety of tires and wheels - all
carefully selected to match and enhance the vehicle's dynamics capabilities.
They include P235/70R16 all-season tires for the XLS and XLT series.
The all-season tires are engineered for improved ride, steering,
noise and fuel economy.
The tires are mounted on 16- by 7-inch wheel designs - varying
from full-face steel and cast aluminum to cast five-spoke aluminum
and chrome full-face steel, depending on the model. |
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