Proper wheel alignment is important for a number of reasons. First of all, a vehicle that is aligned to specs will track straight and steer in the desired direction with more ease. Second, tire wear is minimized when toe and camber are set properly. And, finally, a vehicle that is correctly aligned will brake straight, true and safely. It all proves that wheel alignment is important to optimum vehicle performance.
Camber, Caster and Toe
Vehicles are brought into a shop for a wheel alignment for a number of reasons. Maybe abnormal tire wear has been detected, perhaps the vehicle is pulling or drifting to one side, or maybe new tires have been installed. Whatever the reason, it’s important that the wheels be properly aligned. The Big 3 alignment angles are camber, caster and toe. Below is a definition of each.
Camber is the vertical tilt of the wheel (inward or outward) as viewed from the front of the vehicle. Positive camber is shown in (Figure 1). Excessive camber can cause premature tire wear.
Caster is the vertical tilt of the steering knuckle (forward or rearward) in reference to the position of the lower ball joint and upper ball joint, or strut. It is viewed from the side of the vehicle (Figure 2). Caster is measured in degrees relative to a true vertical center line. Although caster does not affect tire wear, it does affect the stability of the vehicle.
Toe is the inward or outward angle of the wheels as viewed from above the vehicle. It is illustrated in (Figure 3). It is measured in degrees or inches. Toe has a profound effect on tire wear. If toe is properly adjusted, it allows the wheels to travel in the same direction. Front tires are usually toed in as acceleration has a tendency to out the front tires.
SUSPENSION DESIGNS AND ALIGNMENT
Several different front and rear suspension designs are in the FCA US LLC vehicle lineup. This is quite different than the way it was 50 years ago during the muscle car era. Back then, the basic front end consisted of unequal length A-arms connected to the steering knuckle with ball joints. A coil spring was fitted between the A-arms with a shock absorber inside the spring. Tie rod ends were attached to the knuckles to steer the wheels. All rear suspensions were solid axle with leaf springs. Camber, caster and toe were adjustable on the front suspension, but none of the alignment angles could be adjusted on the rear.
Front suspension design changed dramatically with changes to front wheel drive (FWD) and transverse mounted engines. The MacPherson style suspension replaced the unequal length A-arms to allow more room in the engine compartment. This design uses a lower control arm and ball joint plus a strut that, for all intents and purposes, replaces the upper control arm, upper ball joint and shock absorber. The coil spring is mounted around the top of the strut.
Rear suspension designs changed, too. With the widespread use of front wheel drive, the rear suspension, like that on the popular minivans and Chrysler PT Cruiser, is a beam with trailing links, coil springs and shock absorbers. On the vehicles with this design, camber, caster and toe are not adjustable.
Other, more complex, rear suspension designs are used on vehicles such as the new Chrysler 200 (the UF platform) and the Dodge Challenger, Dodge Charger and Chrysler 300 series. These cars use independent designs that utilize multiple links, coil springs, stabilizer bars and shock absorbers. Rear toe is adjustable on these cars, as is camber. It should be noted that camber adjustment on the Chrysler 200 is done in a manner much different than on the Dodge Challenger, Dodge Charger and Chrysler 300.
Before a wheel alignment can be performed, both the front and rear suspension should be checked. Look for damage to any suspension components, worn or cracked bushings, leaking struts and shocks and any abnormal tire wear. Be sure that the fuel tank is full and that the luggage and passenger compartments are free of any items that are not factory supplied. Finally, check the vehicle’s curb height to be sure it is within specifications.
Position the vehicle on the alignment rack and read the current alignment settings on the front and rear suspension. If camber and caster are within specs, check toe. On most FCA US LLC vehicles, the camber and caster settings are determined at the time the vehicle is designed. This is referred to as Net Build (check the appropriate service manual for the vehicle being repaired to verify this fact). As a result, camber and caster are not normally considered adjustable angles on the front suspension. This is true on the minivans, Chrysler 200 and the Dodge Challenger, Dodge Charger and Chrysler 300, among others. If these angles are not within specs, check the suspension for damage.
Note: Do not attempt to adjust wheel alignment angles by heating, bending or by performing any other modification to the vehicle’s suspension components or body.
If individual front camber and caster are found not to meet alignment specifications, each can be adjusted by shifting the engine cradle (refer to TechAuthority.com for specific details). In addition, for some vehicles, such as the Dodge Challenger, Dodge Charger and Chrysler 300, and the minivans, adjustment bolt packages are available to adjust camber and caster.
On the Dodge Challenger, Dodge Charger and Chrysler 300 vehicles, special bolts (one for camber, one for caster) with offset grooves are used to replace the inboard mounting bolts of the lower control arm and tension strut. On the minivans, the lower strut mounting hole is elongated to allow caster adjustment.
When performing an alignment on a vehicle with rear suspension adjustment features, adjust the rear camber first, rear toe setting next, then front toe. On the Chrysler 200 (UF body style), rear camber is adjusted by rotating the mounting bolt and nut on the lower transverse link which has a cam feature. The mounting location to the lower control arm is slotted to allow the adjustment.
On the Dodge Challenger, Dodge Charger and Chrysler 300 vehicles, rear camber is adjusted by installing repair camber links that are available in plus or minus 1mm lengths. A 1mm link will change camber approximately 0.5 to 0.7 degrees.
On many vehicles with adjustable rear toe, this setting is changed by rotating a cam bolt that connects the toe link, as on the Dodge Challenger, Dodge Charger and Chrysler 300 vehicles, to the rear crossmember. The bolt is rotated to obtain the desired toe setting.
Finally, after checking and adjusting the other alignment settings on the front and rear suspension, we can adjust front toe. Remember, adjust left toe first, then right toe. As much as suspension design has changed over the years, front toe is still set by adjusting the length of the outer tie rod end.