Customer satisfaction. That’s the one thing you always want to achieve when you align a customer’s vehicle. Satisfied usually means no steering pull, no steering wander, no steering shimmy, no off-center steering wheel – and no comebacks!
An alignment provides other benefits, too, such as reduced rolling resistance (which helps fuel economy) and reduced tire wear. Most customers won’t appreciate these benefits as much because they are not as noticeable. But as the miles add up, so do the savings.
Achieving the goal of a satisfied alignment customer should be easy. All you have to do is hook up your alignment equipment, check the wheels, and if the wheels are out of specifications, you bring them back into specifications, right? So what happens if the vehicle is out of specifications and there are no factory adjustments other than toe? Or the suspension has been raised or lowered? Or the vehicle is used to tow a trailer or haul plywood?
And what’s the fix if you’ve aligned the wheels to specifications, but the steering still pulls or drifts? Or the steering is still off-center? Or the vehicle feels unstable at highway speeds? Or the tires are still wearing unusually fast? You’re back to square one.
Achieving an alignment that truly satisfies each and every customer may take some extra effort on your part and a willingness to tweak the specs a bit so the wheels can be aligned to match the customer’s driving style and needs.
A LOADED QUESTION
For example, do you align a work vehicle the same as one that is only used for personal transportation? A pickup truck or SUV that is often used as a work vehicle to haul heavy loads will ride lower than one which normally only carries one or two passengers. If you don’t compensate for the extra weight, the alignment you set in the service bay won’t be the same alignment the wheels see when that leaves your shop and is put to work. Camber, caster and even toe can change when there’s a payload in the back.
If you notice a trailer hitch on a vehicle or see obvious signs in the cargo area that it may be used to haul heavy loads, ask you customer what he hauls and how often. Then add some weight to the back and do your alignment. You’ll probably get a better alignment than if you align the wheels with the vehicle empty.
STRAIGHTENING OUT STEERING PULLS
A steering pull should be a red flag for every alignment technician. If a vehicle is pulling or drifting to one side, it obviously needs an alignment. But there may be more to it than misaligned wheels.
For a vehicle to steer straight, it must have:
All four wheels pointing in the same direction. All four wheels must be square to each other and square to the road surface (in other words, parallel to one another, perpendicular to a common centerline, and straight up and down).
All four wheels must offer the same amount of rolling resistance. This includes the “caster effect” between the front wheels that steer.
There must be no play in the steering or suspension linkage that positions the wheels.
If all three conditions are not met, the car will pull or drift to one side depending on which forces are at work.
Checking toe will tell you if the front wheels are parallel to one another, and checking camber will tell you if the wheels are perpendicular to the road. But don’t stop there, because rear toe is just as important as front toe.
Though you may not take the time to check rear toe on a rear-wheel car or truck with a solid rear axle, rear toe should always be checked, just like you should on front-wheel drive cars and those with independent rear suspensions. Why? Because rear toe misalignment or a cocked axle will create a rear axle steer condition that makes the steering pull. A simple front-end alignment will not fix this kind of problem and will leave your customer less than happy with the results.
Rear toe is also different from front toe in that front toe misalignment is self-centering. When the front wheels are toed-in or toed-out with respect to one another, the two wheels share the toe angle equally while rolling down the road with tread wear on both tires being equal. With rear toe, that’s not necessarily the case because the rear wheels are not free to steer nor are they tied together with a steering linkage.
On a car with a solid rear axle, a cocked axle will toe-in one wheel and toe-out the other by an equal amount. The axle will still want to roll straight, causing the rear wheels to dog track to one side. Rear toe wear will not be a problem in this instance, but front toe wear may be because of rear axle steer. Turning the front wheels off-center to keep the car going straight causes the front wheels to toe out slightly.
With an independent rear suspension, one wheel that’s toed-in or toed-out will also affect steering. If toed-in, the wheel will push to the inside. If toed-out, it will pull to the outside. This too, can lead to a dog tracking problem and cause both rear tires to scuff.
The effects of camber on steering are obvious to anyone who’s ever ridden a bicycle. A wheel that leans to one side pulls towards the side it’s leaning. That’s why you don’t always have to steer a bike to turn it. Just lean to one side to change direction. The same is true with an automobile or a truck. If a wheel tilts outward at the top (positive camber), it’ll pull to that side. If a wheel leans in at the top (negative camber) it’ll push in. Therefore, a vehicle will always pull towards the front wheel that has the greatest positive camber or away from the wheel that has the most negative camber.
When you do a front end alignment, setting camber to factory specs is supposed to keep the wheels more or less vertical within the range of normal suspension travel. Depending on suspension geometry, the manufacturer’s alignment specs may call for as much as two degrees of positive or negative camber, with an acceptable variation of up to a degree either way. Needless to say, that can leave a lot of room for error.
The one mistake you don’t want to make is to align every vehicle the same or to your own “rule of thumb” specs. Every vehicle is unique, so you should treat each one accordingly when you align the wheels. The engineers who came up with the alignment specs had their reasons for specifying certain numbers, so start by following their recommendations.
HITTING THE BULLSEYE
When doing an alignment, always aim for the midpoint or preferred setting within a range of acceptable specs. And when that isn’t possible, then make sure you’re at least within the range of acceptable specs.
Also, try to minimize cross-camber by keeping the side-to-side camber readings within half a degree of each other. If camber is not within half a degree side-to-side, it may create a steering pull.
If the wheels won’t align, or if the wheels on a vehicle with a “nonadjustable” suspension are out of range, then something is bent or worn and needs to be straightened or replaced. Don’t just set the toe and let it go. If camber is off the mark, find out why and see if it’s worth fixing. A weak or broken spring, a collapsed control arm bushing, a mislocated strut tower or engine cradle, or a bent strut or control arm can throw camber off as well as Steering Axis Inclination (SAI) to cause a steering pull.
As with toe, rear camber is also important on vehicles with independent rear suspensions. A sagging suspension (typically due to a weak or broken spring) will often cause a rear camber problem, so be sure to inspect the suspension carefully if rear camber is off.
Like camber, caster should be within half a degree side-to-side otherwise the suspension may lead towards the side with the least caster.
Steering wander can sometimes occur if the front wheels have insufficient caster. This may be the case if the front end has been lowered or the rear end raised.
Increasing caster increases steering stability because it forces the suspension to lift when the wheels are steered. The trade-off may be increased steering effort. Decreasing caster reduces steering effort, but also decreases high-speed stability. European luxury cars typically use a lot of caster to make the vehicle feel more stable at highway speeds. But too much caster can make the steering feel heavy and stiff – even with power steering.
Steering pull that’s caused by road crown can sometimes be compensated by adding positive caster to the left front wheel. You don’t need much, just enough to offset the road crown which slopes to the right. The trick is to find the right amount of caster that keeps the vehicle going straight and keeps your customer happy.
If caster is out of range, check for worn strut or control arm bushings, a mislocated MacPherson strut tower or a bent lower control arm.
DON’T FORGET SAI
Related to camber is the Steering Axis Inclination (SAI) angle. SAI is one of the most overlooked angles in alignment geometry. Yet it can cause a steering pull if there’s a difference of more than one degree side to side. Like caster, a vehicle will lead to the side with the least SAI.
The SAI angle is the line along which the steering pivots. On a short arm/long arm suspension, it is the line that passes through both ball joints. On a MacPherson strut-equipped vehicle, it runs from the upper strut mount through the lower ball joint. It is a “nonadjustable” angle that is built into the suspension. Even so, checking SAI can tell you if parts are misaligned when camber is out of range.
SAI also aids steering return. The slope of the steering pivot causes the car to lift slightly when the wheels are turned. The greater the SAI, the more the suspension lifts when the wheels are steered. This aids steering return and helps the steering “feel” more stable at speed. On some front-wheel drive cars, the SAI angle can be as high as 13 to 25 degrees.
The toughest alignment job is the “problem” vehicle that keeps coming back because it’s wearing out tires or isn’t steering straight no matter how you align the wheels.
Sometimes the real problem is undiagnosed collision damage, such as a bent strut, steering arm, control arm, mislocated strut tower, subframe or engine cradle that is affecting alignment. And as we said earlier, rear axle steer may be causing front toe wear, as well as a steering pull.
A problem vehicle may have misaligned structural members that position the front or rear suspension. Assembly line build tolerances have tightened considerably in recent years, but nobody is perfect. Mistakes are made, and the so-called plus or minus 1 mm build tolerance is more myth than reality in many instances.
Some vehicles, especially trucks, just seem to wear tires because of built-in Ackerman problems (or the lack thereof) that prevent the front wheels from toeing out properly when turning. Others may rub the shoulders off the front tires because of high built-in caster angles in the front suspension. There’s not much anybody can do about these kinds of problems short of reengineering the vehicle’s suspension.
One thing you should always do is check to see if the vehicle manufacturer has issued a technical service bulletin on a tire wear or steering problem. Sources for this information include this magazine, Alldata and Mitchell. If you see a tire- or steering-related TSB listed, read it and follow the instructions to diagnose and repair the problem. This sounds like simple advice, but it’s amazing how many times the answer to your problem is only a few clicks away.
Another excellent resource for hard-to-solve alignment problems is the International Automotive Technicians Network (www.iatn.com). Technicians who are stumped can post a problem on this forum so other technicians can offer advice.
DON’T FORGET THE TIRES!
When doing your prealignment inspection, always check tire inflation pressures because a low tire will pull. It’s also important to note tire sizes. A car will pull towards the side with the smallest tires or the side with wider tires. A wide tire offers greater rolling resistance than a narrower tire. Wide tires also tend to be more sensitive to road crown steer than narrower ones. A bias belted tire offers more rolling resistance than a radial, which could also cause a steering pull if someone mixed tire types on the same axle. Because of faulty construction, a radial tire will sometimes take a directional set, creating a pull to one side.
No customer is going to be happy with an alignment if you’ve overlooked worn steering or suspension parts. Worn parts will not hold an accurate alignment, so don’t even try. Worn parts must first be replaced. Then you can align the wheels – and they will stay aligned.
Steering wander can be caused by loose wheel bearings, worn tie rod ends, play in the steering gear, loose or deteriorated rack & pinion steering mounts, or by play in the steering shaft flex coupling.
The alignment of the steering linkage itself is also important. If a steering rack isn’t parallel to the ground or if one of the steering arms is bent up or down, a condition known as “bump steer” can occur wherein unequal toe changes occur side-to-side when the suspension travels through jounce and rebound. This can make the steering twitch or pull to one side when hitting a bump. Measuring and comparing the height of the inner and outer tie rods ends on each side can help you identify this kind of problem.