Wheel Alignment
by Jim Kerr

Have you driven over any rough roads lately? Chances are that you have. Road construction, potholes, broken pavement, and parking lot curbs all take a heavy toll on our vehicle's suspension. Tough as modern suspension systems are, there is always the possibility of something bending, breaking, or shifting out of position. To keep your vehicle in safe driving condition, the suspension should be inspected as part of regular vehicle maintenance.

Getting a wheel alignment is a perfect way to have the suspension checked. During an alignment, the technician starts by checking tire pressures. Then the steering and suspension joints are checked for wear or damage. Steering joints are not allowed any looseness, but the suspension joints may have a small amount of play. The auto manufacturers and aftermarket parts suppliers print specifications for the maximum movement allowed in a suspension part. There are a few vehicles that when jacked up, the joints move so much they appear they would fall off! This may be normal. If you have any doubt about when a suspension joint should be changed, ask to see the inspection procedure and specifications. Good alignment shops always have this information.

During the inspection, the technician may notice leaking shock absorbers or struts. An oil film and dirt on the outside of a shock or strut is considered normal, but oil dripping from the unit indicates a need for replacement. Heavy duty or premium shocks are far superior to the regular units and don't cost much more. They provide better ride and vehicle control and should last longer.

The shocks or struts do not need to be changed to do a wheel alignment, but often a wheel alignment is required after installing new struts because the suspension has to be unbolted. Having the struts changed before an alignment (if required) will save you the cost of a second wheel alignment.

Before connecting the alignment machine, the vehicle's ride height should be checked. The vehicle must be sitting at the proper height for the suspension to work properly. Raising or lowering a vehicle can have a huge effect on vehicle handling because the suspension is working at different angles. The vehicle's centre of gravity will be changed, and change in the roll centre of the vehicle (the point around which the vehicle's body rolls) may cause unsafe handling.

For most drivers, the vehicle should be empty and the fuel tank full while doing an alignment. Remember to remove any sandbags or heavy weight from the trunk. This will allow the vehicle to sit at a normal height and the wheel angles can be adjusted accurately. Drivers that usually haul a heavy load in their vehicle, such as some salespeople do, should keep the same load in their vehicle as they normally have. Trucks used mainly with walk-in campers should have the camper on the truck, if possible, during an alignment. The angles of the front suspension can change a lot when extra weight is placed in the rear.

With everything inspected, the alignment readings can be taken. Four wheel alignment is recommended for most automobiles. The use of independent rear suspension means each rear wheel has to be checked with alignment with the front. The rear wheels play an important part in the way the vehicle steers. If both rear wheels are pointed slightly to one side, the vehicle will travel down the road slightly sideways. You may notice the steering wheel is off centre as you drive. A vehicle that has this problem can be unstable during high speed stops and it also uses more fuel because of higher wind resistance caused by the side of the vehicle pushing the air.

If both rear wheels are pointed outwards slightly (called a toe-out condition) the vehicle becomes unstable during cornering. As the vehicle leans during cornering, the weight is transferred to the outside wheel. The driver has control of the front wheels, but the rear wheel is now pointing outwards and tries to steer the back end of the car around the corner faster. This results in the back end of the car trying to pass the front! This effect is most noticeable on icy roads. Drivers may blame the icy road as the cause of their spin when actually the problem may be incorrect wheel alignment and excessive speed.

On many automobiles, the manufacturer has not made provision for adjusting the angles of the rear wheels, but aftermarket parts suppliers are constantly manufacturing special alignment devices and shims. These can be used on most vehicles to align the wheels for the best driveability.

Having a wheel alignment done is an easy way to have your suspension checked for safety. Decreased tire wear, improved fuel economy, and better vehicle handling are all benefits of getting your vehicle's tires back in alignment.

Camber, Caster, and Toe
by Jim Kerr

Camber, Caster, and Toe. No, it's not the latest craze in square dancing. These three terms refer to the angles of the tires on your vehicle. When you take your vehicle in for a wheel alignment, these are the angles a technician checks and sometimes adjusts.

Correct camber, caster, and toe angles are important for maximum tire life and safe vehicle handling. Even a small error can make a dramatic difference to the way a vehicle drives. Getting a wheel alignment for your vehicle should put everything back into the correct relationship, but why do they change?

Normal wear in suspension parts may cause the angles to change slightly, but major changes are usually caused by impacts or parts failure. Let's look at Camber first. Camber is the tilt of the wheel in or out. Positive camber readings show the top of the wheel is tilted out, while negative readings show the top of the wheel is tilted in. Theoretically, you want the wheel to be at 0 degrees or straight up and down, and most vehicles are close to this, but suspension design or handling demands may require negative caster settings.

Negative camber is usually used on performance cars. During hard cornering, the body rolls to the outside of the turn. If camber settings were 0 degrees, or vertical, the wheel and tire would roll as well, tilting the top out. The tire tread would lift on the inside of the tire, giving less traction and less cornering force. Negative camber settings will move the tire towards the vertical as the body rolls, keeping all the tread on the ground.

Most passenger cars will have camber settings of 0 degrees to about