In previous issues of "Real Answers", we've looked at how choosing the right steer radial can prevent premature removal due to irregular wear.  As we continue looking at the first letter in the irregular wear reducing acronym "S.M.A.R.T." we'll try to get a grip on "selecting" the right drive.

Part of it is selecting the right tire for your drive axles. Notice, we didn’t say “selecting the right drive tire.” Because sometimes the right tire for your drives isn’t a “drive” tire at all.

Why is that?

Most drive tires are designed to dig into soft, wet surfaces, trying to grab, so that the torque of the engine can be transferred to the road. You’re taking upwards of 80,000 pounds of vehicle at rest, and trying to get it into motion.

But what if the road surface is neither wet nor soft? All those aggressive lugs and blocks that characterize most drive tires may be unnecessary.

How can that be?

For best traction and torque transfer, Indy racers use “slicks.” The pavement has to be hard and dry, but slicks maximize the amount of rubber in contact with the road – and the traction that results.

So why does everybody use aggressive lug and block patterns?

Actually, not everybody does. Some fleets that operate in the southern part of the country, or that run routes where they never encounter snow, have had good luck running rib radials in drive positions.

Why use rib radials on drives?

If you don’t have to deal with snow, rib radials can be an excellent choice for drive axles. Even on wet pavement, the traction can be superb. And typically, rib radials have shallower tread depths than lug or block patterns. There’s less tire weight to put into motion.

In addition, contact with the road is more or less continuous throughout the tread face. That means less noise and vibration. And generally, there is less tendency for irregular wear, especially of the “heel and toe” variety.

For some fleets, ribs are just more practical. Especially if they can standardize on a single size and pattern for all axle positions. That can greatly reduce tire inventory.

Finally, rib radials usually have far less rolling resistance than drive radials. That can mean superior fuel economy.

Will any rib radial work?

Not necessarily. You’ll want to test it, on your own vehicles and over your own routes, before making a commitment to rib radials on drive axle positions. Remember that unlike steer and trailer positions, tires on drives are subjected to very high torque. That can cause tires to wear rapidly.

And, you’ll also want to consider the fact that many drivers don’t believe rib radials will give them the traction they want.

       
The Bridgestone M711 features an aggressive traction pattern and open shoulder design for a powerful soft surface grip, and a deep tread for long wear.

         
The Bridgestone M726 drive axle radial offers an ultra-deep (30/32”) tread, with continuous contact shoulders to combat tread element squirm and resulting irregular wear.

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