Wheel Alignment 101
PREFACE: This is very basic article written to help educate the novice mechanic as well as all vehicle owners about the basic terminologies and concepts of wheel alignment.
In addition to this article, there is a brief article HERE that will help you check for component wear and aid in identifying defective steering and suspension parts on your vehicle. This is not a complete list, but it will help you to identify some of the basic problems and some of the most common wear items in the steering and suspension systems.
Next to changing the transmission filter and transmission fluid, wheel alignment is perhaps the most neglected vehicle service on the face of the planet today. Until you hit a curb, and major crater in the street, or another vehicle, almost everyone puts off the yearly visit to the alignment shop unless they are experiencing excessive tire wear. The fact of the matter is, a good alignment is critical and can actually affect your vehicles performance. If you don’t believe this, sit down and watch an automobile race on TV some day. A proper alignment provides the driver better cornering, better fuel mileage and allows the car to be driven more safely on the race track. It will do the same for your street car as well.
Worn suspension components (springs, bushings, tie rods, ball joints, shocks, etc) not only effect the way your car handles, they are also VERY hazardous on any car. Worn components can get you or someone else hurt or killed!!!!
The following definitions will help you better understand how your suspension and steering works and why an alignment is important to your car and to your safety.
The terms that you generally hear are: “TOE IN” or “TOE OUT“.
TOE IN is where the front of the tires are closer together than the back of the tires, like a person who is pigeon toed. Their feet rotate inward towards each other. Cars are always setup with TOE IN because, TOE IN, is used to compensate for the “pull” on the tires created by the car moving down the road. This is called road drag. Almost all cars are set up with a small amount of TOE IN to insure that normal deflection of the bushings, and other steering components are taken up so that the wheels travel down the road with close to zero toe under normal road drag.
TOE OUT is the just the opposite, the front of the tire is further apart. If your car is in a TOE OUT situation, it can make your car wander from left to right and it will be very unstable and hard to control when you are driving it.
CAMBER is the inward (toward center of car) or outward tilt of the top of the tires in relation to the center line of the vehicle. If the tops of the tires tilt inwards, the car is said to have “negative camber”, if they tilt outwards, it is called “positive camber”. The purpose of CAMBER is to provide the maximum amount of tire contact between the vehicle and the road during a variety of cornering situations. The tire can only provide maximum adhesion if all of the tread available is loaded as equally as possible. Many cars are setup with zero or a bit of negative camber, and this negative camber helps to offset suspension deflection and other forces, such as body role, that tend to cause the steering tires to roll over onto their sidewalls.
CASTER, is tough for some people to picture. Simply put, it is where the tires center of drag is in relation to the upper and lower steering point linkage. In other words, a car with “positive” CASTER would have its upper steering linkage (the upper ball joint) behind the lower linkage (lower ball joint). CASTER is measured in degrees and is generally not visible to the naked eye.
Most cars are now set up with “positive” CASTER, this helps to return the wheels to the direction the car is traveling (self centering). This “self centering” action results in a vehicle that feels more stable and tends to wander less.
Just like a car with to much toe out, a car will pull to the side if it has the least amount of CASTER. Too much CASTER causes a slower steering response. CASTER is often toyed with a bit to help or hinder steering response in a car with or without power steering.
Front wheel drive cars generally do not have any CASTER adjustment, because the wheel offset and toe setting are much more critical in a car with inherent torque steer tendencies like most front wheel drive cars have due to their design.
Positive CASTER also improves straight line tracking because the CASTER line (the line drawn through the steering pivot when viewed from the side) intersects the ground ahead of the contact patch of the tire. Just like a shopping cart caster, the wheel is forced behind the pivot allowing the vehicle to track in a straight line.
Two Wheel Alignment:
The term Two Wheel Alignment is a process where both front wheels are aligned to provide the best Toe in, Caster and Camber settings to provide the best all around handling and tire wear under normal driving conditions.
Four Wheel Alignment:
The term Four Wheel Alignment is a process where both front and rear wheels are aligned. In a typical Four Wheel Alignment, the rear wheels are checked for toe and tracking.
In a typical situation the Rear wheel “Toe” is adjusted by adding or removing small shims between the rear wheel hub and the rear axle. On our T-Bird’s and Cougars it is done buy using offset bushings.
Tracking is checked with a series of electronic gauges and the rear axle is check to make sure that it “tracks” properly behind the front wheels.
On a Four Wheel Alignment, the adjustments are first made to true up the rear alignment, then the front is adjusted. Therefore a full Four Wheel Alignment will cost more because there is a lot more work involved.
NOTE: Getting an alignment done on a car with worn or defective steering or suspension components is a waste of time and money. It will NOT correct the instability and poor drivability inherent to worn steering and/or suspension components.
ANY alignment shop that tells you that they will do there best to align your car with the bad or worn parts still on the car should be avoided AT ALL COST!!!!