backlit image of car and mechanic performing wheel alignment

What is wheel alignment?

Wheel alignment is adjusting the wheels to point straight ahead (toe), not to lean to either side (camber), and to maintain stability (caster). Some adjustments can be made using adjusters built into the car. Other adjustments are made by inserting or removing shims between the frame and suspension components.

Not all wheel alignment angles are easily adjusted. On many cars, there is no way to adjust caster or camber, and when an alignment angle is found to be out of specification, other steps must be taken.

One possibility is loosening suspension bolts, prying the component in the desired direction, then tightening the bolts. Another possibility is the use of aftermarket shims or adjusters to add adjustability. If none of these options will work, whatever component or components are bent must be replaced.

How is alignment measured?

Wheel alignment can be measured in a number of ways. Solutions such as string (just like in your kitchen drawer) and bubble gauges (sort of like a level) can be used. In fact that’s how they taught it when I was in school. However, 30 years later most shops are using advanced laser measurement or photometry equipment.

We use a Hunter DSP600 for our alignments. Hunter equipment is found in Toyota, Honda, and Subaru service centers. It offers the fastest setup and most accurate measurement of any system we investigated. It was also the most expensive, but with the time saved during the alignment setup, we will eventually recoup the extra cost while providing our customers with very accurate alignments.

Do I need an alignment after replacing tires?

You will find many tire stores that recommend aligning your car every 6 months. In our opinion this is a waste of money unless you own some seriously exotic and expensive tires.

That said, most people replace tires every four years or so. We think that’s not an unreasonable interval for wheel alignment.

But then again we’re making payments on a $50,000 alignment machine, so maybe we’re biased. You’re welcome to do whatever you’d like. No pressure as always.

do I need wheel alignment?

The only way to know if you need an alignment is to have your alignment checked. However, there are some things to watch out for.

If your tires wear unevenly, that’s a sign the alignment may be out. Unfortunately it comes a little too late to prevent the wear that has already occurred, but if you notice uneven tire wear you can still get an alignment and prevent additional premature tire wear.

Pulling can be another symptom of misalignment, but it’s not the only possible cause. Tire conicity can also cause a pull or drift.

Tire conicity can be caused by wear due to misalignment, so it might be the reason your car still pulls after alignment. You can test this theory by swapping the front tires left to right to see if the pull changes directions. Or we can check it using our road-force machine.

If your car pulls to the right after alignment, be sure to consider the road crown. Find a truly flat road to drive on (which actually isn’t all that easy if you’re driving on the right side of the road). If your car pulls to the left after alignment, there may be a tire issue causing the pull.

Do you need an alignment after replacing struts?

We strongly recommend an alignment after replacing struts, even if there’s no camber adjustment on the strut or knuckle. There’s very little chance that a replacement strut made in a different factory many years after the original strut was manufactured will be exactly the same as the original.

How much does a wheel alignment cost?

A basic alignment usually sells for about 1 hour. How much is that? I stopped putting prices on the web a long time ago because they change and I don’t come back to edit pages frequently enough to keep up.

When I started at Art’s our hourly rate was $55/hour. Now it’s $158 per hour. What will it be when you read this? Who knows. Give us a call.

But wait. What does “basic” alignment mean. It implies there’s a non-basic variety, right?

An alignment includes adjusting all adjustable angles. But sometimes parts are bent, and either need to be replaced, or we need to come up with another way to compensate for the damage.

If the car went barreling over the center median a 50 MPH, we might not be able to adjust it with the factory adjustments built into the car, in which case it may cost more to get the alignment back into specification.

What is 4 wheel alignment?

Two wheel alignments are a thing of the past. 4-wheel alignment is the only type of alignment these days.

Cars and trucks had solid axles prior to the late 70s and the only adjustable alignment angles were in the front. When shops started investing in alignment equipment beyond string and bubble gauges, they started advertising “Four wheel alignments” because it was something not all shops could do and it set them apart.

These days it’s equivalent to a hotel advertising “Color TV”. Yeah. All the hotels have that, and nobody cares because they have a phone, tablet, or laptop with them and the TV is useless in comparison.

That said, some cars don’t have adjustable alignment angles in the rear. However, the rear alignment is always measures and the front wheel alignment will be optimized to work well with the rear.

This is sometimes referred to as a “thrust alignment”. Even though the rear wheels are adjusted, the front wheels are aligned to point in the same direction as the front.

Alignment angles

What is toe in wheel alignment

Toe, simply put, is direction the wheels are pointing. Zero toe would be perfectly parallel wheels pointing straight forward. Toe-out means the front of the tires are farther apart than the rear of the tires. Toe-in means the front of the tires are closer together than the rear of the tires.

Toe has different effects on tire wear in the front and in the rear. When the front wheels are toed out, the inside edge of the tire scuff and wear out early. When the front wheels are toed in, the outside edge will scuff and wear out early.

Toe angle’s effect on rear tire wear

On the rear of the car toe has a different effect. It usually causes diagonal cupping wear pattern whether the tires have too much toe in or too much toe out. The diagonal cups are caused by the tires hopping and skipping along the road.

It’s hard to explain why, but I’ll give it a try. Draw an overview of a car with 4 wheels on a piece of paper, make the front wheels parallel, but toe the rear wheels in substantially (say 45 deg. in just to make the demo easier) Now draw lines parallel with the rear tires following their path of travel if they were to roll.

You will notice that the lines you have drawn intersect. Since the tires are attached to the car they can not intersect. Instead they roll a bit, then skid outward, roll a bit, then skid outward again. This goes on and on until the tires have diagonal cups worn into the treads where they have been skidding outward.

What is camber angle

Camber is the lean of the wheel. If the top of the wheel tilted away from the car, that is called positive camber. If the top of the wheel is tilted in towards the car, that is called negative camber.

Camber can cause a pull to one side or the other depending on the direction of the lean. The car will pull in the direction of the wheel with the most positive camber. However, if both sides have the same amount of negative or positive camber, they will cancel each other out and the car will not pull. Camber can cause premature tire wear, but is not as hard on tires as toe is.

Caster

Caster is the hardest to explain of the three commonly adjusted alignment angles. I like to use the motorcycle analogy. Lots of positive caster is like the forks on a chopper; the wheel is far in front of the support for the wheel.

No car that I know of uses negative caster, so I’ll describe less positive caster as like the forks on a regular street bike, the wheel is only slightly in front of the support for the wheel. Caster will not affect tire wear, but it can cause a slight drift if it’s not equal on both sides.

Caster is an angle that only applies to the front (steering) wheels of a car. The more positive caster is, the more stable the car feels, especially at higher speed. More positive caster also improves steering wheel return.

Caster and steering wheel returnablity

To help understand what steering wheel return is, try this experiment: next time you turn a corner, let go of the steering wheel when you are done turning. You will notice that the steering wheel spins back to the centered position.

Without positive caster, the steering wheel would stay turned until you manually turned it back to the center position. The only downside to lots of positive caster is it make the car hard/slow to steer. The reason positive caster adds stability, steering wheel return and increased steering effort is the weight of the car is trying to straighten the wheels.

You may notice on some luxury cars with lot of positive caster (and powerful power steering) that the front of the car will rise when the wheel is turned to the side, and sinks as the wheel comes back to center.

Thrust angle

The thrust angle is the direction the rear tires are pointing in relation to the center of the car.

Toe Out on Turns

Toe out on turns is a measurement that is used to check for a bent steering arm on the knuckle. It is an angle that will cause premature tire wear, and can sometimes be the source of unexplained premature tire wear on a “perfectly aligned car” since it is not normally checked during a standard alignment.

Toe out on turns can also can cause excessive tire squealing when cornering. When the car is driving in a circle, the outer front tire will be traveling in a larger circle than the inner front tire, it therefore will need to be held at a slightly shallower angle to roll without scuffing. This difference in angles is built into steering arm on the knuckle.

There is no adjustment for toe out on turns. If there’s a problem the knuckle must be replaced. When toe out on turns is off, there is almost always a collision the the car’s past.

Included angle

The included angle is a diagnostic angle, like toe out on turns. It is calculated using the camber measurement and the SAI measurement.

The included angle is built into the design of the car and is not meant to be adjusted. When we suspect there may be some bent parts, we check that the included angle is equal side to side. If not, there’s likely a bent knuckle or strut.

Set Back

This is another diagnostic angle. It’s basically the distance between the front and rear tires. When set back is off and other angles are OK, the body / frame of the car usually needs to be repaired or straightened.

alignment head to “toe”. An explanation of wheel alignment.