A Straight Line to Performance

Actually, alignment doesn't necessarily mean straight. Alignment, the proper toe, caster, and camber for the four wheels that your Fiero rides on, is often misunderstood and simply confusing to many. The alignment, however, can have a significant affect on how your car steers and how the tires wear. These in turn can affect how the car handles and brakes. The trouble is, many owners rarely think about wheel alignment. They don't know from one car to the next what should be done, how it should be done, and when it should be done. Your car may require an alignment after one season of pounding through potholes; an annual event of the Midwest winter games. The Owner's Manual, Maintenance Schedule booklet, and Do-It-Yourself manual that came with your Fiero don't even mention wheel alignment. Even the Haynes Manual's who, what, why, and when of wheel alignment don't help much. The Haynes Manual states (page 228, copyright 1989, Haynes North America): "Wheel alignment refers to the adjustments made to the front suspension and steering components to bring the front wheels into the proper angular relationship with the suspension and the road. Such variables as the angle of the steering knuckles from the vertical, the toe-in of the front wheels, the tilt of the front wheels from vertical, and the tilt of the suspension members from vertical affect alignment. Front wheels that are out of alignment not only affect steering control, but also increase tire wear."
"Rear alignment refers to the angular relationship between the rear wheels, the rear suspension attaching components and the road. Camber and toe-in are the only adjustments required."
"Obtaining the proper wheel alignment is a very exacting process that requires complex and expensive machines to perform the job properly. Therefore, it is advisable to have a properly equipped shop align the wheel immediately after you do any work on the front or rear suspension pieces for any reason."
Well�that was�um�helpful. Are all of your questions about alignment answered? No? Okay. What we can discern from this discourse is that the wheel alignment involves various adjustments to the suspension and steering. It involves front and rear suspensions so therefore you should have a four-wheel alignment performed. And since this is an "exacting process" requiring specialized equipment and skills, you won't be doing this in your garage at home, which explains why the Do-It-Yourself manual doesn't give you any instructions.
First, we need to understand the terminology, which often sound like so much techno-babble, but is not really difficult to understand. Our Fieros have an independent front suspension with unequal length control arms. It has shock absorbers and coil springs. The control arms are attached to the frame with bolts and bushings and to the steering knuckle/front wheel spindle assembly with ball joints. The rear suspension, components shared with the front of the GM X-body cars (Citation, Phoenix, Omega, Skylark) is a MacPherson strut (strut inside the coil spring) with the upper ends bolted to the vehicle and the lower ends bolted to the knuckles. The lower control arms are bolted to the engine cradle. We also need to know about toe, caster, camber and thrust angle. It is important to note that although the 1988 Fieros had a redesigned suspension, the general design is the same with redesigned components.
Toe is usually expressed as toe-in or toe-out. Toe refers to the way the front of the front wheels point toward the centerline of the car, toe-in, or away from the centerline, toe-out. It would seem that the proper setting would be neither toe-in nor toe-out, because too much adjustment either way causes the tires to scrub as the car moves down the road. That is, the tires are both rolling and being pushed at an angle across the pavement. When a car's toe is excessive, you can hear the tires squealing as it proceeds in a straight line. It is the same as a tire squealing around a corner at high speed. The tire scrubs or slips across the pavement. Obviously this would result in uneven tire wear. Too much toe-in and the inner shoulder and circumferential rows of treads wear excessively. Too much toe-out and the outer side wears. Most front wheel drive cars have some toe-out and most rear wheel drive cars have some toe-in. Proper toe settings are the most critical for proper tire wear. On many cars, the rear wheel toe can also be adjusted. Our Fieros ('84-'87) are specified to have toe set at +0.15 +/- 0.1 degrees per wheel at the front and the rears. The '88 Fieros, which have a modified suspension are specified to have +0.3 +/- 0.2 degrees per wheel in front and 0.15 +/- 0.1 degrees per wheel in the rear.
Caster is the forward or backward tilt of the wheel relative to the vehicle. For instance, a shopping cart has negative caster; the wheels follow behind the vehicle. Negative caster is unstable. Give a shopping cart a shove and it is liable to take out some groceries as it goes careening down the aisle. Positive caster, as found on the front wheel of a bicycle, allows the vehicle to keep going in a straight line, even with our hands off of the controls (fine for your bicycle, not so good to do while driving a car). Without some positive caster, a driver would constantly be sawing at the steering wheel to keep the car moving in a straight line. Positive caster keeps a car moving straight. You only need to turn the steering wheel to change direction. Positive caster also assists the front wheels, and therefore the steering wheel, in returning to center or straight ahead after changing direction. This is particularly important for non-assisted steering, like that of our Fieros. Although caster does not affect tire wear, variation in caster from one side to the other can result in a vehicle drifting in one direction constantly. This condition will require constant steering corrections. Our Fieros are specified to have caster set at +5.0 +/- 2.0 degrees for 1984 through 1987 cars. The 1988 Fieros are specified to have +5.0 +/- 0.5 degrees. Interestingly, the ASE Manual states that this caster setting is for "GT & Formula" Fieros. For "manual steering" equipped Fieros it lists a caster setting of +3.0 +/- 0.5 degrees.
Camber is the inward or outward tilt of the tops of the wheel at its vertical centerline. Positive camber is when the tops of the tires tilt toward each other, or the tops are closer together than the bottoms. Negative camber is when the tops of the tires tilt outward, away from each other. Zero camber would place the tire tread parallel with the pavement. Positive camber will place more pressure on the inboard portion of the tire. Improper camber usually only results in wear on one tire, not both. Weak springs can greatly affect camber. Camber can be adjusted on the rear of cars with independent suspension. Our Fieros are specified to have a front camber setting of +0.5 +/- 0.8 degrees and a rear camber setting of -1.0 +/- 0.5 degrees for '84 through '87. The '88 again have separate settings of 0 +/- 0.5 degrees for front and -1.0 +/- 0.5 for rear.
Thrust angle is the difference between a front wheel alignment and a four-wheel alignment. Simply put, thrust angle is the direction the rear wheels are trying to make the car move due to the rear axle not being parallel to the front. Front wheel alignment is based upon the centerline of the car and assumes the centerline is true. If the rear axle is not parallel with the front axle, or in other words when the rear axle is not perpendicular to the car's centerline, one rear wheel is farther back from the front than the other rear wheel. This configuration will try to steer the car to the side that has the one rear wheel set back farther. The driver will be required to turn in the opposite direction to maintain a straight progress. If you've ever followed a car that appears to be driving straight down the road but moving slightly sideways, or dog-tracking, you have seen a car with the rear axle that is not perpendicular to the centerline of the car. This misalignment of the rear axle is often the result of frame damage from a wreck. A four-wheel alignment is a must for front-wheel drive cars and any vehicle with an independent rear suspension, and is also acceptable for rear drive cars so the front wheels can be adjusted to compensate for misalignment of the rear axle.
The cost of wheel alignment, and even the additional cost of a four-wheel alignment, will save you that much and more in tire life. So inspect your tires and suspension components regularly. Monitor you Fiero straight-line handling. If you detect a problem or if you've changed suspension components, wheels or tires, it probably wouldn't be a bad idea to have a four-wheel alignment performed.

(Source: Chicago Tribune, ASE Manual, Haynes Manual, Paul Vargyas)

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