By Jim Kerr
With the longer service intervals and better reliability of newer vehicles, it is easy to forget that our cars and trucks still need regular maintenance. Perhaps we don’t need a tune-up every spring and fall any more, but getting a wheel alignment done on your vehicle should be part of your annual maintenance schedule. Rather than thinking of it as an expense, think of it as cheap insurance, as it can save you money in the long run.
There are two types of alignments still offered by most shops. The two-wheel alignment checks the front wheels only, while a four wheel alignment checks that of all four wheels. Two wheel alignments are most often done on rear-wheel drive vehicles with a solid rear drive axle, but even on these vehicles a four-wheel alignment is the preferred method and the most common type of alignment done today.
Before an alignment is performed on your vehicle, a technician does a pre-alignment inspection. This would include checking tire pressures, checking the vehicle ride height to detect sagged springs and checking for wear on the suspension ball joints, steering joints and bushings. If any of these are worn, they should be replaced or repaired before the alignment is performed or the alignment won’t stay in adjustment.
The technician also looks for a possible load in the cargo area. A loaded vehicle will change the alignment angles. If your vehicle frequently carries a load, you should mention it to the technician and bring the vehicle in for an alignment with a typical load. That way the angles can be adjusted with the load in place. I remember one customer who came back a couple times saying his truck still didn’t steer right. After the third time, we discovered he was loading a camper on the truck when he took the truck home. By having him bring the truck in for an alignment with the camper in place, we were able to correct his steering problems.
With everything inspected, the technician will install an electronic gauge on each wheel and calibrate them. The alignment computer will then display the camber angles on each wheel. Camber is the tilt in or out of the top of the wheel. A tire should sit almost straight up and down so the tread wears evenly, although some performance vehicles will have the wheel tilted in slightly about half a degree to improve cornering performance. When the vehicle’s body rolls in a corner, this causes the wheel and tire to move closer to vertical for better traction.
The technician will also measure caster. Caster is measured as the change in angle of the wheel as it turns through an arc. The technician will turn the steering wheel to the left and right and back to centre to measure caster. Caster affects steering response. More caster will make the vehicle more stable in a straight line, while less caster will make it turn into corners more easily. Each manufacturer has different caster specifications for vehicles based on their suspension design, powertrain design, weight, wheelbase and performance characteristics.
Toe is the third angle the technician is looking for. Zero toe means the tires are pointed straight ahead. More than about 1.5 mm toe-in or toe-out will wear tires quickly, so adjusting this angle accurately can save you money in tire wear and in fuel economy due to reduced drag.
Of the three angles, many vehicles have adjustments for camber and toe on the front suspension and some have adjustable caster too. Independent rear suspensions sometimes have fewer adjustments, although for vehicles without factory adjustments there are often aftermarket kits that will allow the angles to be changed.
While the vehicle is being aligned, other angles are automatically checked. One is called included angle or king pin inclination. This is an angle set by the suspension design and if it is out of specification it indicates bent parts. Perhaps you have hit a curb hard or a big pothole; the technician can then identify where the damage is located.
A wheel alignment can detect problems before they become serious or unsafe, and can also increase tire life and fuel economy. Spring is the ideal time to have an alignment done, as winter’s rough roads are history and dry summer pavement can wear tires faster, especially if the alignment is incorrect. This is preventative maintenance that can actually save you money.