We’ve come to the letter “R” in our irregular wear-reducing acronym, “S.M.A.R.T.”
It stands for “Rotate tires, if necessary, to equalize wear.”
Tire rotation can be an effective method of equalizing tire wear. And,
there are some new developments in rotation that can extend tire life even more.
We’ll be looking at several different options that may be effective for you.

Should we be rotating our tires?
Maybe. Some fleets, like those that use single drive axle tractors, may find their drive tires wear very evenly throughout useful tread life. If that’s the case, rotating drive tires may not produce any benefit. So you might as well save the time and expense.

How do we know we should rotate our tires?
Basically, there are several criteria. First, are you experiencing irregular tire wear? That is, is one part of some of your tires worn more than other parts? With certain types of irregular wear conditions, rotation can be very helpful in equalizing wear over the whole tire.
The second question is, are some of your tires wearing faster than other tires on similar positions? For example, most fleets note that the driver’s side steer tire tends to wear faster than the one on the other side.
And tires on tandem drive axles often wear at different rates, depending whether they’re on the front or rear axle.

When should we take action?
You probably should establish some guidelines that work for you. Some fleets rotate tires when there’s an overall tread depth difference of 4/32nds between tires on equivalent positions. That is, if the driver’s side steer has 4/32nds less remaining tread depth than the other steer, they’ll swap positions.
Other fleets, for convenience, base rotation on mileage and PM schedules. If they do maintenance every 15,000 miles or so, they may do tire rotations at every other PM, that is, at 30,000 miles. If you need to remove tires for any reason, it may be an opportunity to rotate them.

Can rotation “erase” irregular wear?
Not in the sense of reversing it or correcting it. What rotation can do is change the way that irregular wear forces are applied to the tires. In some cases, the irregularity can be “scrubbed out.”
But it’s important to remember that you can’t reverse irregular wear – or cure it – by rotation. All you can do is equalize the overall wear pattern.

For example?
One common type of irregular wear is “heel and toe” wear on block-type drive tires. Usually, the edge of the block that touches the road first (the heel) wears slowly, while the edge that touches it last (the toe) can wear much faster. The result can be blocks that are worn at an angle
Heel and toe wear is rarely a problem in itself, but can lead to more serious alternate block or “pumping” wear, a good reason for taking corrective action.

Tread blocks can develop excessive wear on the edge that touches the road last. Called “heel and toe” wear, changing the direction of rotation can sometimes counteract these patterns.

By reversing the direction of the tire’s normal rotation, the forces involved are reversed, and the faster wear is transferred to the other side of the block. The irregular wear forces are still there, but the overall wear is more equalized.

What about “toe” problems with steer tires?
If you have a slight “toe-in” condition, the outer ribs of your steer tires may wear faster than the inner ones. There may be rounding on the outside edges of tread elements and “feathering” on the inside edges.
By swapping sides with these tires, assuming that you have not corrected the toe-in condition, again, you may be able to “scrub out” the irregularity in wear.

Why wouldn’t we correct the toe condition?
It might be very slight. It might not be convenient or economically feasible to correct it right away. You might be too busy to take the vehicle out of service.

What if we do correct it?
In that case, rotation might not have much effect. Since the irregular wear was caused by a misalignment condition to begin with, once proper alignment is restored, forces scrubbing out the wear irregularities may be absent or insignificant.

Are there other kinds of tire rotation?
The most common type is cross-rotation, where tires are swapped from one side to another of the vehicle and where tires on tandems are also swapped between axles.
There’s also what we might call “move-back” rotation.

Partially worn deep tread drive radials, like the Bridgestone M726
can provide lots of extra service when moved back to trailer positions.

“Move-back”?
With very deep drive radials, like the Bridgestone M726, with 30/32nds original tread depth, once these tires wear down to about 12/32nds or so, you may want to please drivers by replacing them with new tires, especially as winter approaches.
Many fleets, reluctant to grind away all that remaining tread on the retreader’s buffer, are moving these drive tires back to trailer positions, getting many more useful miles from them before sending them for retreading.
Since many trailer tires only have 12/32nds on them to start with, it’s almost like having new trailer tires. [For more details on this technique, see Real Answers, Volume 2 Issue 2, page 12. If you don’t have a copy, find it on the Internet at www.trucktires.com]

What if we’re using the same tires in all positions?
A number of fleets are simplifying tire selection and inventories by using rib radials all around.
What seems to work well is to run these tires for about 30,000 miles or so, then swap the steer pair with those on the left rear tandem. If an additional rotation is needed, the steers (previously drives) can be swapped with the tires on the right rear tandem. For convenience, repaired tires can be placed on the front tandem.

So we’d be rotating tires from drive positions to steer?
A number of fleets have tried this with excellent results. While we don’t know exactly why this works so well, it could be that the torque of drive axles helps “break in” the tires (a bit like breaking in a new pair of shoes, perhaps) creating a very even wear pattern – that continues throughout the life of the tire.

Are there tires that shouldn’t be
rotated?

Not really. Even unidirectional tread pattern tires (like the Bridgestone R227) can be rotated successfully. In that case, though, you’ll need to demount, flip the tire and remount, in order to keep the unidirectional pattern in the direction of travel, for maximum irregular wear resistance. Remember that rotation is a technique for equalizing wear. It won’t cure or reverse an irregular wear condition. That can only happen when you find and fix the cause.