The steer tire of the future
The steer tire of the future will most likely boast fewer ribs, straighter grooves and simpler tread patterns as truck tire manufacturers continue to pursue lower rolling resistance and the minimization of irregular wear, says Roger Stansbie, director of tire technology, Commercial Division, for Continental Tire the Americas LLC.
“We, as an industry, are about to do some serious homework to fine-tune steer tires.”
Stansbie says the bulk of the work will focus on two areas: irregular wear and energy efficiency.
“Everybody is playing around with different forms of decoupler grooves, and on pure long-haul applications, that’s still going to be the resolution in the U.S. — having some form of decoupler groove in the shoulder whereby we can reduce the stiffness modulus and take a lot of resistance to movement out of the footprint.”
Manufacturers also are experimenting with different shoulder widths as a means to even out stress points in the tire’s shoulder area. “I think with the move to more fuel-efficient tires, there has been a lot of emphasis put on reducing the number of grooves in the tire while still keeping an eye on wet traction.”
For instance, Continental’s premium steer tire, the Continental HSL2, boasts four grooves, down from the six grooves found in the Continental HSL Eco Plus several years ago.
“The more grooves you have, the more disruptions you will have during the molding process.,” says Stansbie. “The more disruptions you have during the molding process, the more you are in danger of not getting an even, consistent distribution of material across the tread.
“If you go with too many grooves, you run the risk of not getting the best distribution of material. Then you’ll end up with uneven pressure distribution, and if you have uneven pressure distribution, you’ll get uneven wear.”
No more zig-zags?
The California Air Resources Board ruling that requires certain trucks and trailers operating in California to use U.S. Environmental Protection Agency SmartWay program-approved tires has thrust low rolling resistance and energy efficiency into the permanent spotlight, says Stansbie.
“If you’re not on the SmartWay list, you can have the best-wearing tire on the market but you won’t get into long-haul (fleets) that have to go into California. And we have caught wind that other states are looking at (similar regulations).”
Due to the emphasis on fuel efficiency, Continental engineers estimate they will have to improve the rolling resistance of the company’s truck tires by at least 15% every five years.
They expect to achieve this through the development of new compounds and the simplification of tread patterns.
“The more disruptive the tread pattern to linear orientation — driving forward — the more disruption you will have from a rolling resistance point of view,” says Stansbie.
“What we’ve found is the fewer the ribs, the better, and the straighter the grooves, the better. In other words, a zig-zag pattern is no longer going to be featured in the future. If you look at a lot of the new generation tires coming out — not just steer, but drive and trailer — they almost look like aircraft tires, (with) hardly any zig-zag at all.”
Stansbie warns that such a dramatic change in tread patterns may be difficult for some end users to accept because they are accustomed to “chevron-style” patterns, and associate such configurations with maximum stability.
“But they will have to get used to it because anything that disrupts the movement in the footprint can end up using more energy and reducing fuel efficiency.” ■
Three questions... about steer tires -- Miles to removal still number one, says Purol
“Miles to removal remains the most important criteria to evaluate steer tire performance,” says Richard Purol, vice president of Treadways, which is promoting its new Sumitomo ST778 steer tire. CTD recently caught up with Purol to discuss the latest trends in the steer tire category.
CTD: What are the hot trends in steer tires?
Purol: Today’s long haul tractors are required to operate in a broad range of conditions. Steer tires need to be durable enough to be bumped around during pickup and delivery at either end of the haul and wear smoothly while running down the road at high speeds for long periods.
CTD: Are decoupling devices becoming more prominent?
Purol: Decoupling grooves do help control the start and migration of irregular wear and pretty much define a tread design as a long haul steer. However, experience has taught us that their use and configuration has to be balanced against operating conditions and vehicle characteristics.
CTD: What can tire dealers do to raise awareness about the importance of steer tire maintenance?
Purol: Most fleets seem to realize that a manufacturer that gets the steer tire right probably makes very good drive and trailer tires, as well.
“That said, we can’t remind fleets to manage air pressure often enough.”