I mentioned in my March 1 Tire Business column that sales of new trucks and trailers are burgeoning now and are expected to continue through 2006.
As tire experts, your fleet accounts will no doubt be asking you for recommendations on tires they should specify for these new vehicles. Due to space limitations, I didn't touch upon the aspects of tread selection in that column.
Obviously this is a major consideration and often the hardest decision to make, since selecting the proper tread design for an intended application is critical to obtaining the maximum potential of the tire and the lowest tire cost per mile.
Last important decision
Tread design selection is usually the last decision you make when selecting a tire. However, it is as important a decision as choosing the casing type, tire and wheel size and operational characteristics since it can affect fuel economy, traction and noise generation.
Truck tire tread patterns are usually designed to address a variety of needs in general applications. Sometimes you may have to sacrifice one performance requirement in order to obtain others of greater priority.
For example, some over the road tires with deep treads are designed for high mileage, resistance to penetration and good wet traction.
However, if the fleet needs to emphasize fuel economy in its operation, you may have to select a tire design that has a shallower tread depth and a less aggressive tread design that may reduce traction and overall mileage.
Therefore, it is important to prioritize the fleet's tire needs based on its vehicle's application requirements before you go any further. A list of typical tire requirements is as follows:
* Long tread wear;
* Long, high-speed run;
* High fuel economy;
* Resistance to irregular wear;
* Good steering response;
* Good dirt and mud traction;
* Good dry traction;
* Good wet traction;
* Good snow traction;
* Resistance to penetration;
* Reduced noise generation;
* Short/intermediate on-off road;
* Long/intermediate on-off road;
* Resistance to cutting/chipping;
* Resistance to stone retention; and
* Resistance to rib tears and curbing.
Since the selection of tire characteristics is always a tradeoff, tires designed for specific axle positions have become popular. That approach takes advantage of new materials, processing or design technologies.
This has made tire selection a bit easier, but there are still a few general guidelines you can follow once you know which characteristics are most important to your fleet customer.
Rib designs, used primarily on steer and trailer positions, have grooves that run circumferentially around the tire.
They can be zigzagged or fairly straight. Zigzagged grooves offer more biting edges for traction on wet city streets and, since they reduce the effects of side forces, they are ideal for turning and maneuvering in pickup and delivery operations. Continuous straight grooves roll in a straight line with little rolling resistance, which is ideal for high-mileage, high-speed, fuel-efficient, line-haul operations.
Highway steer tires generally have deeper tread depths, while highway trailer tires generally have shallower tread depths. Shallower tread depths make trailer tires more resistant to irregular wear and more fuel efficient.
Defense grooves-also known as decoupling grooves, stress-relief grooves and shoulder-pressure distribution grooves depending upon the tire manufacturer-are thin, straight grooves on the shoulders of the tire that act as barriers to reduce shoulder wear on rib tires. These grooves are excellent in over-the-road operations but do not perform well in urban use since they are prone to stone retention and tearing as a result of curbing.
They are also usually found in steer tires rather than in trailer tires that are subjected to curbing and scuffing.
Lug designs used primarily on drive axles have blocks and grooves that cut across the tread pattern, adding traction and aggressiveness to the tire. They also can have some circumferential grooves as well, either in the middle of the design or on the shoulder.
Wide shoulder ribs that are resistant to side forces permit the use of deep treads that provide long tread life in line-haul operations. These tread designs also are known as closed shoulder patterns.
Open shoulder designs that have blocks on the shoulder as well as throughout the pattern have more aggressive traction qualities for operation in rain, mud and snow. Aggressive lug type tires can tend to feel less stable laterally or squirmier than solid circumferential rib designs. Lug tires with closed shoulder patterns fall somewhere in between.
Tire manufacturers today produce tires specifically designed for tandem-axle-drive and single-axle-drive trucks and tractors.
Tires on single-axle-drive configurations usually need more traction qualities as well as more rubber since they are very effective buffing machines.
However, the fleet should be aware that deeper tread depth tires tend to feel less stable than comparable shallow tread tires. In extreme cases, stability complaints can result, especially on single-axle-drive units.
Lug tires with shallower tread depths resist the squirm that constant turning in short-haul operations creates and are less prone to irregular wear patterns.
Some tire manufacturers offer unidirectional tread patterns that are designed to rotate in only one direction.
They are specifically designed to reduce irregular wear in high-mileage operations; however, some special efforts must be made to ensure they are installed correctly on vehicles.
That often can be a challenge for fleets. (Fleets should be aware that if unidirectional tires are installed backwards, only a loss of mileage would result. No damage will be inflicted on the casing.)
Sipes and ``stone ejectors'' are attributes that can be found in both rib and lug tires. Sipes-tiny notches along the edges of tread grooves-are molded into tread designs to help relieve rolling stresses that initiate and spread river/erosion wear.
They are essential in tread patterns of over-the-road tires, so you should look for their presence in any tread pattern you are considering for this type of operation.
``Stone ejectors'' or ``platforms'' are specially designed, groove-side angles or nubs at the base of tread grooves that can reduce stone retention and actually work to eject stones before they get lodged in the tread.
This attribute is important in operations that run over gravel or poor asphalt roads where casing damage and irregular wear caused by stone retention is a problem.
Conduct a test
All the variations in tread designs tire manufacturers are now producing can provide maximum performance in certain applications but minimal performance in others. Thus, it is important to provide help to fleets in selecting the right tread designs for their operations.
Don't hesitate to sit down with your fleet accounts and provide them with good advice.
However, since newer designs rely heavily on sophisticated rubber compounds to provide good wear, handling and fuel economy, it is more difficult now to predict tire performance based on appearance or tread depth alone.
Always encourage the fleet to run a tire test to ensure the tire selected really does meet its requirements. This can be done by having the fleet spec a group of new vehicles with one make and model of tire while having another group fitted with a comparison tire.
Then you'll have the ``opportunity'' to assist your account in overseeing the tire test.
Does it ever end? You're a commercial tire dealer. The answer is, ``No.''