What causes irregular wear on trailer tires?

All tires are subject to irregular wear, but we notice it mostly on slow-wearing tires. With fast wear, irregular wear gets scrubbed away before it becomes noticeable.

Often, irregular wear is the result of uneven pressure, most common at the edges of ribs. It’s not a fault in the tires or their treads. It’s just the nature of things.

Rib edges are the places where irregular wear tends to start, especially when side forces are present.
Defense Groove™ structures on the R195F create tiny ribs that sacrifice themselves to protect the larger ribs beside them.

Why are the edges so susceptible?

The edge of a rib is where pressure against the road must suddenly go from normal to zero. In addition, these edges bear the brunt of side forces resulting from turning, road crown, wind, misalignment, etc.

Edges can be dragged across the pavement by side forces, creating abrasion – the seed of irregular wear.
But the wear spreads all over the tread, not just the edges.

That’s part of the problem with irregular wear. Non-uniform pressure tends to create irregular wear, and irregular wear tends to create non-uniform pressure. So, once irregular wear starts, it usually spreads.

That, incidentally, is why you can only prevent irregular wear – or equalize it by rotating tires. Once it starts, you can’t stop it or reverse it.

How can irregular wear be prevented?

It helps to use shallow treads, usually just a half-inch or less. With shallow treads, tread elements and edges are very stable, very stiff, and less subject to side forces.

Imagine a pencil eraser. When it’s brand-new and fairly long, you can bend it easily. But once it’s worn down, it’s much harder to distort.

Just as a worn pencil eraser bends less than a new one, shallow tread elements on trailer tires distort less, making them more resistant to irregular wear.

Is that what makes the R195F work?

That’s part of it. But the R195F also incorporates several irregular wear-protection features. The first is the addition of Defense Groove™ structures at both tread edges.

Same as on steer tires?

Yes. This design has been very successful in combating the initiation and spread of shoulder edge wear on steer radials.

As tires wear, the “defense rib,” the tiny outer rib created by the Defense Groove structure, wears more rapidly than the shoulder rib beside it, and “sacrifices” itself to protect the larger rib.

The R195F incorporates Bridgestone’s Defense Groove design at the shoulders. The small, outermost rib wears away rapidly, “sacrificing” itself to prevent the initiation and spread of shoulder edge wear on the rib beside it.

What other irregular wear-fighting features are on the R195F?

The R195F also has Equalizer Rib™ structures alongside the two main ribs. This is a patented feature, first offered on the R227 steer radial.

Like the Defense Groove design, these small ribs divert irregular wear forces from the ribs alongside them, sacrificing themselves to promote even wear.

Just as the Defense Groove design creates a small, sacrificial rib that protects the shoulder, Bridgestone’s patented Equalizer Rib structures provide similar protection for the ribs beside them.

What about the center rib?

Irregular wear on the center rib is usually not a problem. The pressure across the center rib is remarkably uniform, even with side forces present.

However, you will notice that the ribs on the R195F have hundreds of tiny notches along their edges.

The R195F’s irregular wear-fighting features also include extensive siping along the edges of each rib to relieve rolling stresses that can cause irregular wear.

What do the notches do?

The edge of the tire’s ribs, like the tire, is curved. But, when forced into contact with the pavement, it is compressed into a flat, straight shape. This causes stress at the rib edges.

The small notches, or rib edge sipes, allow the rib edges to conform to the road surface with less stress, and less potential for irregular wear.

What other features does the R195F have?

The R195F also has thick sidewall protectors to fight damage from curbing, cuts and abrasions.

All Bridgestone radials with the letter “F” in their models feature sidewall protectors that resist damage from curbing. Both sidewalls are ribbed, so when one rib is worn away, the tire can be reversed for continued protection.

How does this work?

The sidewall protector rib is just an extra-thick layer of rubber guarding the relatively thin sidewalls against curbing damage.

With today’s longer trailers, especially in urban hauling, tires are often scrubbed against curbs and other obstacles that can seriously damage sidewalls.

With protector ribs on both sidewalls, if one rib is worn away, you can reverse the tire on the wheel to expose a new set of protector ribs for continued protection.

Any differences for retreading?

The R195F, like every Bridgestone radial, is designed and built to be retreaded.

And, in the case of the R195F, it has been designed with an extra-wide tread base, so that 9-inch pre-cure retread stock can be used.

These 9-inch retreads are favored by many fleets for drive tire retreading, for which the R195F is completely suitable.

What sizes are available?

The R195F is available in both standard and low profile sizes for 22.5 and 24.5-inch wheels. All carry a “G” (or 14-ply) load rating.