Wheel alignment a crucial check for spring

Hey there, time traveller!
This article was published 13/03/2009 (6054 days ago), so information in it may no longer be current.

I am looking forward to spring and the disappearance of slippery, rutted streets and roads, as I suspect many of you are, too. Unfortunately, winter takes a harsh toll on our automobiles, with everything from rusty body panels to damaged suspensions. One of the maintenance items you should have done on your vehicle at least once a year is a wheel alignment. It may be OK, but this gives you the opportunity to have a technician inspect the suspension and check the vehicle steering angles to ensure everything is in good operating condition.

A wheel alignment can be done at many auto repair shops and tire shops, but it does require specialized equipment that may cost $15,000 to $25,000, plus a drive on hoist, so not all shops do them. However, if you have a favourite repair shop that doesn’t have the equipment, they will usually sublet it out to another shop, so you still deal only with your favourite shop.

Before doing an alignment, a technician will inspect the vehicle’s suspension for damage. If something is wrong, there is no sense in performing an alignment until after it is corrected. Damage can come from hitting a curb or pothole, or bouncing over rutted lanes. A vehicle suspension is tough, but if it takes an impact in certain directions, it is fairly easy to bend parts slightly. There may not be any visual indication of damage, so the technician will go ahead with the alignment.

The technician inspects ball joints, steering joints, springs, suspension rubber bushings, shocks and tires for wear. Some of these such as suspension bushings are inspected visually, but other items such as ball joints have maximum-wear specifications in the repair manuals. If they are not worn beyond specifications, they don’t need replacing. Even springs have specifications. In this situation, the technician measures the ride height of the vehicle to see if the springs are supporting properly. If the ride height is too low, the springs have sagged and should be replaced. Also be sure to remove any heavy loads from the trunk such as sandbags or this will affect the vehicle ride height.

Tires do not need to be replaced to have a wheel alignment done, but if they are badly worn or worn in an unusual pattern, the technician will usually recommend replacement. A wheel alignment won’t even out the wear on badly worn tires, but it will keep new tires from wearing faster than they should. Tire pressures are also adjusted during the alignment so the vehicle is sitting properly on the alignment machine.

Now the technician connects electronic sensors to each wheel and reads the information out on the computer monitor of the alignment machine. To measure some angles, the technician will turn the steering wheel both ways and then back to centre. Initially, they are looking for camber and caster readings. Camber is the tilt of the tire in or out at the top. For general driving, most vehicles have the tire sitting close to vertical when driving down the road. Caster measures the angle of the steering pivots at the wheel. Positive castor makes the vehicle steering more stable, while negative castor produces quicker steering response. Camber and castor are not adjustable on many vehicles without installing additional parts specifically made to allow adjustments. These angles are set at the factory as part of the body and suspension design and should be good unless there is some damage or worn parts.

The technician will also check other angles called toe-out on turns and kingpin inclination. These are preset suspension angles and if they are incorrect, they indicate damage — usually something is bent slightly, so the technician will then determine which parts need replacement.

Finally, the technician checks toe. Toe is the amount the tires are pointed in or out at the front. The desired Toe angle is zero or slightly toe-in while the vehicle is driving down the street. To accomplish this, the vehicle may actually be adjusted with slight toe-out while it sits stationary, but this changes to near zero as the vehicle drives. Too much toe-in or toe-out will wear tires quickly. Think of it like walking with one shoe dragging sideways. The dragging shoe (or tire in this case) wears much faster. You won’t notice too much toe-in except by watching the tire wear, but excessive toe-out can create an evil handling vehicle.

Finally, you may find two wheel alignments or four wheel alignments offered. Always get a four wheel alignment. This checks the angles on all four wheels and also makes sure the vehicle drives with the body straight down the road.

Jim Kerr is an experienced mechanic, instructor of automotive technology, freelance journalist and member of the Automobile Journalists’ Association of Canada.

kerr.jim@sasktel.net