Hey, youíre out of line
Dennis R. FranklinYuma, AZ
Franklin's Tire and Suspension
With the advent of front wheel drives and more sophisticated
alignment equipment the old "front end alignment" is obsolete.
The manufacturers require a Thrust Alignment or a 4-wheel alignment, not
to be confused with 4 wheel drive trucks. If you have a front wheel
drive vehicle the manufacturer probably recommends a 4-wheel alignment,
thrust at a minimum. If itís a pickup or you have an older car, it
will probably require a thrust angle. All manufactures give a range
from and to, with a preferred setting for "normal driving". If
you use your vehicle outside of those perimeters the preferred settings
are only a place to start Ėnot stop. If you tow, alter the
suspension, put on different tires and wheels, use the vehicle strictly
around town, load it or you have a wear or handling problem that is
different, then "preferred" settings are in order. So before
you get an alignment remember these tips.
- Think twice about having an alignment done at a shop if they donít
ask any questions and just say, "give me your keys".
- Be prepared to explain just what it is that makes you believe the
alignment is out. Without a symptom there is no problem.
- Make sure the fuel tank is full. Alignment specs are setup with
that in mind
- Ask around to find out whom to go to. Your friends and the people
you come in contact with should be able to tell you both where to go
or not to go.
Ok, why thrust angle and what was wrong with the old "front-end
alignment". It all has to do with the equipment doing a much more
precise job. In a nut shell, the old equipment read the position of the
opposite tire, left to right and right to left. The new equipment
references the position of rear tires plus the fronts. Now lets move on
to angles and specifications. All manufacturers give a range, from and
to with a preferred setting. The preferred setting is for 1 and Ĺ
people, full tank of gas and "normal" driving. (Iím still
trying to find out what normal driving is). If you use your vehicle
outside of those perimeters, the preferred settings are only a place to
start Ėnot stop. A good alignment man will ask a lot of questions
before he starts his test drive. Yes, to do it right the car is driven
before and after the alignment. Remember those 9 little things I
mentioned that can cause a vehicle to pull? That and many other things
will be checked during the test drive. If the tech doesnít drive it
this doesnít mean he wonít do a good alignment, he just might not
fix your problem.
Now, lets take a look at those funny numbers and angles. Camber- is
measured in degrees and refers to the top of the tire leaning in or out.
If the wheel is leaning outward it is positive camber; leaning inward
and you have negative camber. Positive camber is normally designed into
the car to add more stability, road isolation and transfer the bearing
load towards the inside bearings. Because of this your vehicle may wear
the tires on the outside and be normal. Donít be too alarmed, the loss
to tire life is measured in just a few thousand miles therefore most
vehicle manufactures deem that as "acceptable ". Put on
negative offset wheels or wider tires and everything changes. If you
change to a different type of tire than the one that came with the
vehicle, do nothing but hard stops, load the vehicle with more than
"normal" loads and Preferred specs go out the window. A good
alignment man will always want to see the old tires, read them and ask
questions relating to the use of the vehicle. His job at that point is
to balance or compromise camber angles to give the customer the best of
everything. This is not an exact science and requires years of
experience to master. There are two other angles that relate to basic
alignments. Caster and toe in. Caster is a driving angle and generally
will not cause tire wear. Without going into details, caster along with
another angle, SAI (steering axes inclination), causes the steering
wheel to return. It also gives the vehicle directional stability. Works
just like the front wheel on a bicycle. You turn the handlebars and the
top of the tire leans into the turn (camber). Ever ride a bike with your
hands off the bars? Thatís directional stability provided by caster.
But because caster causes the tire to lean it can cause tires to wear on
the shoulders. Put on wide tires or wheels that stick out and, you
guessed it, preferred specs goes out the window. Simply stated, caster
needs to be adjusted to fit the configuration of the vehicle as well as
the use of the vehicle, preferred specs are not for everyone. The last
angle is called "toe". If you point your shoes together,
pigeon toed, you are toed in. Stand at attention with your shoes
pointing out at a 45-degree angle and you are toed out. This is by far
the most critical angle there is.
To toe or not to toe that could be the question.
As I stated, toe is the most critical angle. In fact itís so
critical that the spec. range for most cars is less than a ľ of an
inch. This example should give you an idea. If I took an average size
tire and cut the tread off, split it and laid the tread flat on the
ground. For every 1/8 of an inch that the toe is out that piece of tread
will be dragged 8 feet sideways. A brand new 80,000-mile tire can get
totally worn out in 5000 miles if the toe is out ľ inch. So much for
mileage warrantees. But just like the other angles, toe can be sensitive
to vehicle height and loading. So if you have tire wear problems more
than likely itís a toe problem. Remember I said height sensitive,
which means if you raise or lower a vehicle the geometry has changed and
that includes toe. A good alignment man will ask questions, read the old
tires and test-drive the vehicle.
In summery there is some very good equipment out there that can walk
a moron through an alignment. And to complicate things there are fewer
and fewer good alignment technicians in the market place. (I wonít go
into those reasons now) So no matter where you are, if you need some
work done on your vehicle just ask around; ask anyone you come in
contact with. It could be a waitress a check person at the grocery
store, anyone. And pretty soon one establishment will be mentioned more
than any other. Donít rely on a chain store name as a sign of quality;
rely on what the locals say.
Remember that this report is provided as a free public service of
this web-site. The author is not an employee of either provider and has
no association with either. Information is considered to be accurate to
the best of our knowledge. As of the above date the information is
Copyrighted, the sole property of the author, and unauthorized
reproduction is prohibited.
Dennis R. Franklin
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To take apart the nail clippers,
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