Suspension & Wheel Alignments
While having this service performed on your vehicle is often simply referred
to as an “alignment” or “wheel alignment”, it is actually a complex operation where
your cars suspension angles are measured, and a variety of suspension components
are being adjusted. Think of getting an alignment like a suspension system “tune-up”.
Alignments influence not only the operation of a vehicle’s tires, but also the way
the vehicle handles and steers.
"Out-of-alignment”, occurs when the suspension and the steering system are not
working at their desired angles. In older vehicles, these conditions are most often
caused by spring sag or suspension wear (bushings, ball joints, etc.) Another way
to put the suspension out of alignment is an impact with a pothole or curb. Incorrect
alignment usually results in more rapid tire wear.
When should you get an alignment check?
The alignment of your vehicle should be a) checked whenever new tires or suspension
components are installed, and b) whenever unusual tire wear patterns appear. You
should also consider having your alignment checked after your vehicle has encountered
a major road hazard or curb.
What type of alignments are there?
There are three different types of alignment that we at Herb Gordon Nissan Services
offer and they are front-end, thrust angle, and four wheel.
A front-end alignment only adjusts and measures the front axle angles. Front-end
alignments are okay for some vehicles with a solid rear axle, but checking to make
sure that the front tires are positioned to track directly in front of the rear
tires is also important. Most cars need more than just a front end alignment.
Thrust Angle Alignment
The thrust angle alignment is used to make sure the front and rear wheels are
tracking correctly on a solid rear axel vehicle. Our technicians here at Herb Gordon
Nissan Service would perform the alignment to confirm that all four tires are “square”
with each other. This type of alignment also identifies vehicles that would “dog
track” while going down a road with the rear end offset from the front.
The four-wheel alignment is appropriate for vehicles with four-wheel independent
suspension, or front-wheel drive vehicles with adjustable rear suspension. This
type of alignment “squares” the vehicle in the same way that a thrust angle alignment
does. There is more work involved, as this procedure includes adjusting and measuring
the rear axel angles as well as the front. This is the most common sort of alignment
What does an alignment adjust?
There are four primary static suspension angles that should be measured and adjusted
and those are the caster, camber, toe, and thrust angle. Here are the definitions
of each of these angles and the influence they have on the vehicle.
The angle that we call "Caster" is used to tell the forward or backward slope
of a line drawn through the upper and lower steering pivot points, when viewed directly
from the side of the vehicle. Caster is expressed in degrees and is measured by
comparing a line running through the steering system's upper and lower pivot points
of your steering system, to a line drawn perpendicular (straight up and down) to
the ground. Caster called "positive" if the line through the steering points slopes
towards the rear of the vehicle at the top, and "negative" if the line slopes towards
the front of the vehicle.
Why isn't caster the same on all vehicles? Caster angle settings allow the vehicle
manufacturer to come up with the correct balance of steering effort, high speed
stability and front end cornering effectiveness that they want to achieve. Increasing
the amount of positive caster increases steering effort and makes for better straight
line tracking, and improves the vehicles high speed stability and provides more
effective cornering. Positive caster also makes the tire lean more, when cornering,
as the steering angle increases.
When a vehicle doesn't have power steering, it makes it harder to steer when
the positive caster is increased. Besides that though, positive caster provides
steering improvements by increasing the lean of the tire when the vehicle is cornering
while returning it to a more upright position when driving straight ahead.
The angle that is called "Camber" tells how far the tires slant away from vertical
when viewed directly from the front or back of the vehicle. Camber is measured in
degrees of tilt from the vertical. Camber is called "negative" when the top of the
tire tilts in towards the center of the vehicle and "positive" when the top of the
tire leans away from the center of the vehicle.
The suspension angle called "Toe" measures the exact direction the tires are
pointed compared to the centerline of the vehicle when viewed from directly above.
Toe is expressed in either degrees or fractions-of-an-inch, and an axle has "positive
toe" or "toe-in" when if you run an imaginary line through the centerlines of the
tires, the lines intersect in front of the vehicle, and have "negative toe" or "toe-out"
when they spread apart. Toe settings are generally used to help compensate for the
suspension "give" built in for ride comfort, in order to help tires wear longer.
Toe can also be used to adjust the vehicles handling.
A front-wheel drive vehicle "pulls" the vehicle along through the front axle,
resulting in forward movement of the suspension arms against their bushings. So
most front-wheel drive vehicles use some negative toe-out to compensate for the
movement, so that the tires can run parallel to each other at speed.
But a rear-wheel drive vehicle "pushes" the car and the front axle's tires as
they roll along the road. Because the tires make some resistance when they roll,
this causes a little "pull" or "drag" toward the back of the car, which results
in a rearward movement of the suspension arms against their bushings. So most rear-wheel
drive vehicles use some positive toe-in to compensate for the movement, so the tires
to run parallel to each other at speed.
Why is adjusting toe important?
The vehicle's toe is one of the most important settings in an alignment as it
relates to tire wear. A toe setting that is just a little off its correct setting
can mean a big difference in how your tires wear. If the toe setting is just misadjusted
by 1/16-inch off, each tire on that axle will scrub almost seven feet sideways every
mile! As an example, that translates to the front tires "scrubbing" in a sideways
motion over 1/4-mile during every 100 miles you drive! Incorrect toe robs you of
tire life, and negatively impacts handling.
The thrust angle is an imaginary line drawn perpendicular to the rear axle's
centerline. It compares whether the rear axle is lined up with the centerline of
the vehicle. It also tells if the rear axle is parallel to the front axle and also
that the wheelbase on both sides of the vehicle is the same.
If the thrust angle is not correct on a vehicle with a solid rear axle, sometimes
more than an alignment is needed, it might need a trip to the body shop to straighten
the frame and position the rear axle correctly.
If a vehicle has independent rear axles, (also called independent rear suspension)
it can have incorrect toe-in or toe-out on both sides of the axle, or may have toe-in
on one side and toe-out on the other. This can be adjusted in an alignment.
The suspension on each side of the vehicle is adjusted individually until it
is at the correct toe setting for its side of the vehicle. Incorrect thrust angles
can be caused by either an out-of-position axle, or incorrect toe settings. So in
addition to the handling problems brought about by incorrect toe, incorrect thrust
angles could cause the vehicle to handle differently when turning one direction
vs. the other.
The vehicle manufacturers' alignment specifications generally provide for a "preferred"
angle for camber, caster and toe. The correct thrust angle is always zero. The manufacturers
also provide the acceptable "minimum" and "maximum" angles for each of the specifications.
The minimum and maximum camber and caster specifications typically result in a range
that remains within plus or minus 1-degree of the preferred angle. If an alignment
can't get the vehicle to the recommended settings, sometimes replacing worn suspension
parts is the way to get the vehicle in alignment.
Getting an accurate wheel alignment is the most important step to balance the
wear and performance your vehicle's tires deliver. And getting wheel alignments
on a regular basis will usually save you as much in tire wear as they cost, and
should be considered part of your vehicles routine, preventative maintenance. It
really is like getting your suspension system "tuned up".