Bridgestone South Africa

Where Does Alignment Fit In?

While alignment can be a high-tech process involving lasers and computers in the hands of exerts, one of the best tools for diagnosing alignment problems, is at the end of your arm. We will now discuss some very low-tech techniques that can help you identify areas that need high-tech attention.

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Drive and trailer axle misalignment tend to cause far more irregular wear problems than steer axle misalignment.

How important is front-end alignment on trucks?

As we pointed out in the previous article, the real question is: if misaligned, which axle causes the most irregular wear? 

In the previous article in this series, we emphasized that drive axles seem to cause the most trouble, with trailer axles not far behind. Steer axles are usually the least troublesome.

Why is that?

It may be that steer axles get more attention than drivers or steers. And steer misalignment tends to affect wear only on steer tyres, while drive or trailer misalignment can create wear problems on every tyre position.

How do we know when axles should be aligned?

Some fleets routinely align vehicles as part of the maintenance process. Others do it only when a wear problem develops. We recommend a regular programme of checking tyres for irregular wear, then taking follow-up action as necessary.

But once irregular wear appears, isn’t it too late?

Not necessarily. You can sometimes catch a problem in its early stages and correct it. And often, tyres can be rotated to other positions to “even out” wear. (We’ll discuss that later.)   

You can often feel irregular wear with your hand before you can see it on the tread surface.

How can we detect irregular wear?

One way is to “feel” it. If you run your hand across the surface of a tread, first one way, then the other, you will feel the edges of the tread elements. And, what you feel may tell you more than what you see.

How is that?

When a tyre is new, the edges of the tread elements are usually very well defined – you might say “sharp”. Over time, those sharp edges are rounded off by wear. Chances are, you’ll be able to feel the difference before you can see it.

What should we do?

Run your hand back and forth across the tread. If the wear is even slightly uneven, you will probably notice the edges of the tread elements on one side are more “rounded” – or less sharp – than on the other.

What does that mean?

Remember: “Rubbing Makes Round”. The side that is rounded (or less sharp) is the side where the rubbing force was applied.

Just as this tile distorts this block of foam, irregular wear forces tend to distort tread elements, rounding one side more than the other.

How does that help?

Tyres run best and longest in a straight line. Any time a tyre is not in straight-line travel, wear forces concentrate on one side. This happen constantly during turns, but it can also happen when you’re not turning, because of misalignment. Imagine the tyre is stationery, and it’s the road that’s moving. If the tyre isn’t aligned with the direction of travel, the road “rubs” tread elements on one side more than on the other.

If you know which side is rounded, and how the tyre was mounted, you may be able to tell a lot about the alignment.

For example?

If the right side of the tread elements is more rounded than the left, the tyre was turned a bit to the left. Remember: “Rubbing Makes Round”. 

When you compare two tyres, you can learn even more. If the right steer tyre is rounded on the right, and the left is rounded on the left (more wear on the outside edges of both tyres), you probably have a “toe-in” condition. If both have more wear on the inside edges, you probably have a “toe-out” condition. And, when you align a vehicle, make sure the settings end up not just “in spec” but “to spec”, the middle of the manufacturer’s suggested range.

How do we know how much to adjust the alignment?

The test we’ve suggested won’t tell you that. You’ll have to rely on your alignment expert. Nevertheless, this kind of checking, which takes only a few minutes, can help you catch wear before it becomes a big problem, and can help you decide what to do when you align.

How so?

First of all, whenever alignment is done, insist on a complete report of what the shop finds when they check the vehicle. You need to know where you are, compared to manufacturer’s specs, before you adjust.

For example, if your alignment check shows a toe-in condition, and tyre wear confirms it, you’ll have a pretty good idea what to do. On the other hand, if toe is set to spec, or it you discover a toe-out condition, but tyre wear points to toe-in, there may be something else causing the wear, perhaps a bearing or suspension part – or even a mis-mounted tyre.

Why not just bring everything to spec?

Sometimes, the “It ain’t broke, don’t fix it” rule applies. There are lots of variables, including caster, camber, toe and Ackerman, and they can interact. We suggest you only change a setting if you’re reasonably certain it will correct a problem.

Why go to all that extra trouble?

Because specs have tolerances, and Murphy’s Law says tolerances will sometimes accumulate in a direction that maximizes trouble. If everything’s in the middle, that’s much less likely.

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If steer tyres are more worn on their outside edges, excessive toe-in is likely. If the wear is on the inside edges, toe-out is probable

Also, bear in mind that alignment equipment has tolerances too, so if you’re on the edge of the range, you may actually be outside it because of the tolerances of the alignment equipment itself.

And, once the alignment is done, be sure to get a report on the final settings. This, plus the initial report, should be filed with your vehicle maintenance records. Once irregular wear starts, it can’t be reversed. (You can sometimes stop it or equalize it, as we’ll see in the next section.) So, if you put on new tyres and the problem does not re-occur, what you did worked. If the irregular wear returns or worsens, you’ll have to look somewhere else.

Consult the equipment manufacturer and your alignment provider for details on front-end and total vehicle alignment.

Bridgestone South Africa

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