Bridgestone South Africa

How Can I Improve My Odds Of Getting Even Wear?

One of the biggest challenges faced when fighting premature tyre removal, is the loss of tyres, due to irregular wear.

Which tyre design wears most evenly?

It all depends. No two situations are absolutely identical, and no one tyre will wear evenly everywhere you use it.

For example, a tyre with a tread compounded for on-highway use may not perform as well off the road. And vice versa. In fact, irregular wear is often a sign that you're using the wrong tyre for the job.

What causes irregular wear?

On the inside of the back cover of the S.M.A.R.T booklet, you will find a S.M.A.R.T. "fishbone" type chart, listing 6 different categories and some 36 different causes of irregular tyre wear. And those are just common ones. There are many others, and they all can act together in different combinations. That's why there is no single tyre that is best for every application.

How can I narrow my selection?

One good way is to start by looking at axle position and type of hauling. In this section, we'll focus on steer axles.

Just about everybody uses rib tyres on steers, but even within that category, there are many to choose from. Knowing your type of hauling can help. For example, here are some characteristics of long distance line hauling:

  • Very slow tread wear
  • Minimal scrubbing
  • Relatively high speeds

Why is tread wear slow for long distance haulers?

Tyres are designed to roll in a straight line. And long distance line haulers tend to drive in nearly straight lines - most of the time. Since wear is caused by abrasion, and since there's very little scrubbing, slipping and dragging in line haul operations, overall tyre wear tends to be slow.

How does that affect tyre choice?

For steer axles, tyres with straight (or nearly straight) grooves should perform well. When the grooves between ribs are straight, the tyre naturally tends to roll in a straight line, requiring little steering input to keep it that way. That means very little steering-related scrub, and long, slow wear.

But don't zigzag grooves produce better traction?

Not necessarily. Zigzag grooves provide "biting" edges that can be helpful in slicing through water and road films, but there are other ways to accomplish that. Besides, one of the functions of a groove is to provide a channel for removing water from the tyre footprint. As you might expect, especially at higher speeds, its harder to push water through a zigzag groove than through a straight groove.

So how do you get high traction with straight grooves?

Early in tyre history, John Sipe found a real answer for increasing traction. He cut thin slits into the tread surface. Today, those slits bear his name. Sometimes, these "sipes" go all the way across a rib from groove to groove. Sometimes they are tiny s-shaped cuts in the middle of a rib. Or they may look like tiny notches or nicks along a rib edge. Sipes can improve wet traction on tyres with straight groove designs. Not only that, but sipes can also improve a tyres wear characteristics.

Radials with straight grooves, like the Bridgestone R227, often perform well in long distance line hauling.Extensive unidirectional siping removes water efficiently for high wet traction

The Firestone HP 3000uses zigzag grooves, rather than extensive siping to enhance traction.This design tends to perform equally well in regional or urban hauling where turns are frequent or in long-haul operations.

How do they do that?

A tyre's normal shape is round. But as it rolls through its footprint, this round shape is temporarily flattened - over and over again. This creates tremendous stresses in the tread that can cause it to run hot, wear quickly or wear in an irregular pattern. Sipes break the large shape into hundreds of smaller shapes, greatly relieving these stresses. The result is fewer places for irregular wear to start and spread.

Then why make a tread with zigzag grooves?

For one thing, you can use fewer sipes with a zigzag design. That can mean a simpler, less expensive mould and lower-cost tyre. In addition, even though sipes tend to be very thin, hundreds and hundreds of them add up to a significant amount of rubber that is not there to make contact with the road. In high scrub situations, with more rubber in the footprint, abrasive forces are distributed over a wider area, weakening them. Couple that with tread, compounds designed to resist scrub, and you can experience greatly enhanced tread life in severe wear situations.

But wouldn't a scrub-resistant compound be good for long distance line haul treads too?

Not necessarily. It might generate too much heat at prolonged highway speeds. That could accelerate tread wear and even reduce retreadability.

So what's the conclusion?

On steer axles, whether you're a long distance line hauler, or a shorter-distance operation, you'll probably find that either tyre will work for you. One would have to run a test program for your specific operation, in order to ascertain the best solution.

Bridgestone South Africa

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