Question:What's the difference between a front-end alignment
and a four-wheel alignment (besides the price)?
Answer:The "completeness" or thoroughness of
the job. A front-wheel alignment only aligns the front wheels.
A four-wheel alignment aligns all four wheels. All vehicles
can benefit from a four-wheel alignment, but it is especially
important on front-wheel drive cars and minivans as well as rear-wheel
drive cars that have independent rear suspensions.
Until a decade ago, two-wheel alignments were the norm for
all cars and trucks. But the arrival of front-wheel drive changed
all of that. It's always been important to align all four wheels
to one another because the rear wheels can have just as much influence
on steering as the ones up front do. But on most rear-wheel drive
vehicles, there are no adjustments on the rear suspension. So
even though the need to check rear wheel alignment is there, there's
not much a technician can do if the rear wheels aren't true with
respect to the ones up front.
If the rear axle is cocked slightly to one side or the other,
it creates a "thrust angle" that causes the steering
to pull slightly to one side or the other. If the misalignment
cannot be corrected by repositioning the rear axle, a "thrust
angle alignment" (aligning the front wheels to the imaginary
angle created by the rear axle) can at least make a vehicle steer
straight.
The arrival of front-wheel drive in the 1980s increased the
awareness of the importance of rear-wheel alignment. Though many
of the early front-wheel drive vehicles lacked much in the way
of "factory" adjustments (front or rear!), aftermarket
kits allow most types of alignment problems to be corrected.
Most newer front-wheel drive cars and trucks now have factory
adjustments for the rear suspension.
According to a recent survey by Brake & Front End magazine,
a trade publication for alignment shops, 44% of all alignments
jobs being performed are now four-wheel alignments. Those who
are still doing two-wheel alignments say price is a big issue
with consumers. They don't want to pay more for a four-wheel
alignment. Others say they don't have the proper equipment or
training to do four-wheel alignments.
Two-wheel alignments still appeal to many technicians because
aligning two wheels doesn't take as much time as aligning four
wheels, nor does it require very sophisticated alignment equipment.
A toe stick and a camber/caster bubble gauge are all that's needed
to do a "quickie" alignment job. But aligning only
the front wheels is like asking your dentist to only clean your
upper teeth. All four wheels need to be checked because the rear
wheels are just as important as the ones up front -- even on rear-wheel
drive vehicles with nonadjustable rear suspensions.
