As school bus drivers shuttle students to and from school, their buses encounter potential hazards, including uneven roads, sharp turns and curbs. In addition, frequent stops and starts can take a toll on the bus.
But what part of the bus endures the brunt of this daily abuse? The answer: tires.
SBF spoke with representatives from four tire companies about what makes a tire right for a school bus. Most important, they say, are the physical properties of the compounds that protect the tire from damage, as well as the durability of the casing construction so that retreading is an option.
Goodyear Tire & Rubber Co.
Goodyear Tire & Rubber Co. offers two tires for the school bus market: the G661 HSA and the G182 RSD. The G661 HSA is an all-position tire with a long original tread life, and the G182 RSD drive tire is optimal where enhanced traction is necessary for snowy climates.
The G661 HSA "works particularly well on the steer axle," according to Bruce Woodruff, director, business solutions marketing, commercial tire systems, Goodyear Tire & Rubber Co. "[It] features ... enhanced toughness to protect against sidewall abrasions."
Also, the G661 is equipped with Goodyear's TredLock Technology — interlocking microgrooves that enhance the tire's traction and lifespan.
Both tires are equipped with sidewall protector ribs and scrub-resistant compounds to protect against damage from everyday wear and tear, Woodruff explains.
Woodruff also points out that "retreading is a great way to reduce the cost of a tire program ... a retread costs about one-third the price of a new tire."
Goodyear has 125 authorized retreaders in its network, and its retreaded tires are available through hundreds of commercial tire dealers across North
America, according to Woodruff.
"Goodyear offers a G182 retread that matches the tread design and performance of the new tire," he says. "For bus operators who prefer to run all new tires on their buses, the casings from worn tires can be sold to retreaders, who will retread these casings for other uses."
Maintenance is also an important issue when it comes to tires. Goodyear's fleetHQ network offers school bus fleets a breakdown service, standard pricing wherever fleets operate and consolidated billing through the fleet's local dealer.
Hankook Tire America Corp.
Hankook Tire America Corp.'s "AH24, AH12 and AH11 tires are the most appropriate designs for use on school buses, and work well in all tire positions," says Brian Sheehey, director, commercial tires for Hankook Tire America Corp. "For school buses operated in areas where optimal traction is desired, the Z35A and DH06 tires make good choices for the drive tire positions, while using one of the other three designs on the steer position."
The AH24, AH12, and AH11 tires have tread compounds that are formulated for optimal performance in highscrub applications.
Hankook's tires are built to prevent uneven wear, chips, cuts and tearing. Sheehey explains: "Stone ejectors are located in the groove bottoms to protect the tires from stone drilling. Also, the compounds used in our tires are resistant to ozone cracking and weathering."
When selecting tires for a school bus, Sheehey says safety is key.
"Hankook tires have high standards for endurance and undergo both lab and field testing to validate the expected performance and meet government safety requirements," he explains.
Michelin Americas Truck Tires
Michelin Americas Truck Tires offers several tires that can address the unique challenges of transporting children safely to and from school, according to Doug Jones, customer engineering support manager for the company.
"Our most popular tire for school buses is the Michelin XZE2 all-position tire," he says.
The climate in which a bus is operated affects tire choice. "Buses that operate in difficult winter conditions may choose to take advantage of the Michelin XDN2 drive-axle tire, which delivers superior levels of traction, even in extreme conditions," Jones explains.
Michelin designs these tires to provide the needed levels of traction and responsiveness required to safely operate a bus, as well as withstand the potential for sidewall damage from curb impacts or debris, Jones says. "By using a casing construction and sidewall compound that are more damage resistant, the tires will be better able to endure the rigors of school bus service," he adds.
Some of the tires also incorporate the company's Matrix Spring technology,which helps to provide needed traction and protects the tread by "locking together for the stability normally associated with solid tread blocks," Jones explains.
"It is also important that the tires are properly maintained, especially the tire pressure," Jones says. "An under- or over-inflated tire's performance will suffer compared to that of a properly inflated school bus tire."
Jones also notes that proper vehicle alignment is integral to maximizing tire life, and that school bus operators should avoid using products on a bus' tires that could potentially harm the tire.
Double Coin Holdings
Double Coin Holdings’ RT 500 all-position tire is an especially popular product for the school bus industry, according to Aaron Murphy, vice president at China Manufacturers Alliance (CMA). CMA, the North American subsidiary of Double Coin Holdings, also produces the RT 600 and the RT 606+, both newer generation tires equipped with special tread compounds designed to fight rapid wear.
Each of these tires has sidewall protectors on both sides of the tire, so that if “you retread the tire and one side of the sidewall is worn down, you can turn that tire around and you’ve got a brand new sidewall protector ready for use,” Murphy explains.
“We also have special siping in the tread areas to fight irregular wear, because what occurs in an urban environment … is you’re maneuvering in and out of driveways or over railroad tracks,” he adds. “You want to try to preserve the tread as much as you can.”
This siping also prevents rib tearing. The sipes help to increase tire traction in wet environments, and torn ribs could compromise bus safety or even prematurely end the life of a tire.
In addition, Double Coin tire “casings are manufactured to withstand urban use because … [school bus drivers] are not just driving in a straight line. They’re twisting and turning, creating lateral forces, so the tire has to have a strong casing,” Murphy says.
Double Coin also offers federal, state and local government fleet pricing, as well as over 1,000 points of sale throughout North America.