Keeping vehicles riding true

Jan. 1, 2020
The geometry designed into the steering and suspension system of a modern automobile directly determines how that vehicle will handle under a variety of conditions. Keeping that geometry in specification not only is a matter of following proper align

The tires may be where road contact is made, but it is the steering and suspension components that keep it in the right place.

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The geometry designed into the steering and suspension system of a modern automobile directly determines how that vehicle will handle under a variety of conditions. Keeping that geometry in specification not only is a matter of following proper alignment procedures, but it also is a matter of routinely inspecting the components that keep everything in place. Damage or excessive wear in wheel bearings, ball joints, tie rods and control arm bushings can alter these angles, even allowing them to shift to whatever they want as the car moves down the road.

How's That Car in Your Bay?

Few customers come in asking for a vehicle alignment, but often the telltale signs of one needing correction are obvious when you look at the tires, and that is something you should be doing on every car that comes in. Any wear that is not uniform across the tread should raise suspicion. Don't forget the rear tires! With so many models using independent rear suspensions, you can have a rear tire being destroyed by improper toe or camber settings just as easily and just as quickly as it can happen to a front tire.

In addition to inspecting tire wear, be sure to check for obvious play in each wheel/tire assembly. With the car secure on the lift, raise it to chest high and then grab the tire on each side (at the 3 and 9 o'clock positions) and see if there is noticeable play.
If so, you should suspect an issue in the tie rods on a rack and pinion design, or a problem in the steering linkage on a more conventional model. On some cars (BMW comes to mind), side-to-side play also can be the result of blown lower control arm (rear) bushings.

Follow up by moving to the top and bottom of the wheel (the 12 and 6 o'clock positions) and check again. Play here usually is caused by worn bearing assemblies, but also might be excessively worn ball joints.

To properly check a ball joint, it is best to follow the procedure outlined in the appropriate service information. Just remember that the ball joint being checked must be unloaded either by jacking the car up by the control arm, or by the frame, as specified.

Generally, if the base of the coil spring rides on the top of the lower control arm, you'll need to take the pressure off the joints by placing your floor jack under the control arm and lifting the wheel until it just leaves the ground. Failure to follow the correct method for inspection might cause you to miss a problem that will impact vehicle stability and safety.

Fundamental Angles: Toe-in

A check of the alignment angles should be recommended if tire wear indicates a problem, service work that would alter the existing angles has been performed or as a preventative measure any time the tires are replaced or at every other tire rotation. Tire wear caused by alignment will not correct itself once the wear pattern has begun, so the time to protect those tires is before the wear starts.

Of the three basic steering angles, toe-in (and toe-out) is the one most often corrected. A few reasons for this: Toe is easily affected by road impact (debris, potholes, curbing strikes, just to name a few examples), and on many vehicles, it is the only adjustment the OEM allows you to make.

This angle is a measure of the tire/wheel's longitudinal axis in relation to the vehicle's centerline. In the old days, the specification was given in inches and was a measure of the difference in spacing between the two wheels' front and rear rim flanges.

The easiest way to describe it to your customers is to tell them to look straight down at their feet. Toe-in is a pigeon toe stance; toe-out is an open toe stance. Excessive amounts of either will cause the tire to be pushed down the road rather than roll freely, and will quickly wear a tire to nothing.

If the individual wheel toe-in correction is more on one side than the other, the steering wheel will be off-center to the driver when heading in a straight line. While the machine might say total toe is within specification, that doesn't mean the adjustment is right.

Toe-in or -out is also the last angle you'll adjust in your alignment. To help keep that steering wheel straight, keep an eye on the reading for the wheel you're NOT adjusting as you correct the other.

Keep that side stable as you make your corrections, lightly moving it back to where it started from if it tries to wander. I like to start on the right side of the car and then finish on the left. Use the proper tools to turn those tie rods and be sure to hold your adjustment in place as you lock it down.

Fundamental Angles: Camber

The second most commonly adjusted steering angle is camber. Camber is a measure of the tires vertical tilt in relation to the tire/wheel's vertical plane. If the wheel leans out from the car, it has a positive camber and if it leans in, it's negative.

Generally, a car will handle best when the camber angle meets certain needs. When the vehicle is fully loaded, camber should be slightly positive. When the wheel hits a bump and the tire moves upward in its travel, camber will move to slightly negative.

The purpose of the negative transition is to maximize cornering forces. The outside tire in a turn should be kept at a near zero or slightly negative camber to help minimize tire scrubbing at its contact patch.

But too much of a good thing will narrow the contact area, causing wear on either the outside or inside shoulder of the tire.

Ride height can affect this angle, and in the old days of Ford pick-ups with Twin I-Beam suspension, a lot of techs actually tried to bend the I-beams to correct camber issues that were really caused by worn springs and lower ride heights.

If you run into an alignment where you can't get camber back in specification with the adjustments provided, measure this height before bending anything!

What if the vehicle is out of specification and has no adjustment? Several companies offer update kits that can be installed in place of OE components to provide some adjustment of both camber and caster angles.

On Macpherson strut suspensions, the kit often is a simple matter of replacing the stock strut-to-steering knuckle mounting bolts with ones using oblong shafts as cams. However, remember that these kits shouldn't be used as a Band-Aid repair to try and correct a problem caused by worn or damaged components.

Fundamental Angles: Caster

This angle is what causes the wheel to return to center as you accelerate after a turn. It's the angle of the steering axis in relation to the vertical plane through the center of the wheel. It is measured by first drawing a line along the steering axis (for example, through the center of the upper and lower ball joints) all the way to the ground in front of the tire's contact patch and then drawing another through the wheel's center, vertically, until it hits the ground in the middle of the patch.

The intersecting angle is the caster angle, and the distance from the center line ground point and the steering axis ground point is the amount of caster. (In my old motorcycle days, we called it trail.) All cars have positive caster (the axis intersection is in front of the vertical), and the amount of caster plays a huge role in how the car steers.

The more caster angle a car has, the more disturbing force is required to get the wheel to alter course (or turn). That means stability at speed but greater steering effort required to initiate a turn.

Caster is one angle that is often not adjustable, and might require the use of the kits I mentioned earlier if you've first determined that nothing is bent or broken. A car with caster out of specification, especially on only one side, may be trying to tell you that the strut is bent. You can find out soon enough by taking the weight off of the wheel with the alignment target still attached and turning the strut rod to see if the reading changes.

On vehicles with upper control arms, there are often plugs installed that must first be removed before you can make use of the OE adjustment slots. When you do, make small adjustments to the front and rear of the control arm to bring caster into the green.

Many of the more modern alignment machines are even set up to help by telling you exactly what to turn and how much to turn it.

In my early days, performing alignment checks was more time consuming and often overlooked. Today's equipment makes short work of measuring the present condition of a car's steering geometry, and that means it's a lot easier to perform this service for your customer. You'll help them not only maximize the life of their tires, you'll help them reap the full benefits of the handling characteristics designed in by the OE engineers.


Replacing press fit ball joints

CONTRARY TO the methods of some, a super-sized ball peen hammer and jack stand are not the correct tools to use for installing and replacing press fit ball joints. The first miss can deform the joint's edge and make it nearly impossible to remove, and reinstalling even a bit off center can ruin the slight interference fit. The snap ring many have installed is not the primary method of retention.

Better to use a tool designed for the job, and to use it properly. While some models make access to the joint difficult and require a shop press to do the work, most can be done using any a quality aftermarket ball joint service kit like the one shown in the photos below. After removing any necessary components to allow access to the joint, either grind off the peens or remove the snap ring and apply some good penetrating oil around the joint where it fits in the control arm.

Install the tool using the correct receiving sleeve to insure the tool's forcing screw will apply the pressure squarely to the component. While many of these tools can be used with an impact gun, I always liked to tighten the screw by hand. If I've applied all the pressure I can, I find a sharp rap on the control arm near the joint with a large ball peen will often shock the joint and get it moving. If the ball joint comes out easily you may want to consider replacement of the control arm itself.

Choosing the correct sleeves for reinstallation is just as important. Be sure to start and install the joint square to the hole to prevent excessive wear and tear on the control arm itself. Here, I definitely prefer using a hand tool to tighten down the tool. With the new ball joint fully seated, remove the tool and install a new snap ring (if equipped) or peen the upper lip in four spots, 90 degrees apart.


Bearing or seal?

DON'T JUST consider the front end when thinking about steering and suspension. What goes on in the back is equally important in keeping the vehicle tracking true, and you will even find similar components and adjustments on the back end of many front wheel drive cars.

Even rear wheel drive vehicles have needs. Worn bearings can lead to seal failures and loss of lubrication in the rear end. Leaf or coil springs can weaken over time and impact steering geometry, and of course, shocks can fail or wear out.

No matter what design is used in the back half, always reference the front end alignment to the rear's thrust angle (at a minimum). If there are rear adjustments for the basic angles of toe, caster or camber, explain the need for properly maintaining them to your customer and upsell to a more complete four wheel alignment.

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