Truck And Machinery Drive Belts Perform Better, Last Longer

With more resilient materials and grippier designs, your truck and machinery drive belts are lasting longer and performing better. But they still require routine inspection and replacement.
Truck And Machinery Drive Belts Perform Better, Last Longer
Today’s serpentine drive belts are made of EPDM synthetic rubber that wears much like a truck tire.

When is the last time you checked the drive belt in your trucks or machinery for signs of wear? And what should you look for?

If your vehicle is less than 20 years old, it likely is equipped with an EPDM (ethylene propylene diene monomer) synthetic rubber belt. Mark Lein, project development engineer at Goodyear Engineered Products, says EPDM belts were installed by original equipment manufacturers in the late 1990s and introduced to the replacement market in 2002.

Prior to that, most vehicles had neoprene belts. Neoprene had a life expectancy of approximately 50,000 to 60,000 miles. They also cracked and lost chunks of rubber as they wore.


Old-timers might recall the “three cracks in 3 inches” rule-of-thumb for replacing such belts. If you have a neoprene belt on your equipment, be sure to check it regularly for signs of wear, as well as for grease and oil that can reduce service life.

The advantage EPDM belts have over neoprene is they rarely crack, even after 100,000 miles. As EPDM belts age, they gradually lose rubber – like tires on your truck. “With neoprene, you typically had cracks before that happened,” Lein says. “Now the belt actually is wearing away.”

Loss of belt rubber can cause noise and vibration, often signs of a more serious problem.

“If the belt’s worn, if it’s making noise, there’s something wrong with the drive,” Lein says. “Typically a worn belt is slipping. That either means the belt has run its course or you’ve got misalignment issues; you’ve got an idler bearing going out or a tensioner bearing going out or some other bearing going out on the drive.”

Lein says the main cause of belt failure is improper tension. “If anything needs to be taught to the individual installer and even the shops, it’s that proper manufacturer tension is recommended,” he says. “And when you ignore that, you have issues. Proper installation is critical on any belt application.”

James McGarity, ABDS product manager at Gates Corp., recommends checking belts for wear whenever you do repairs, especially after 60,000 miles for on-road vehicles. “The actual O.E. manuals state to start checking at 30,000 miles,” he says. “But if you’re working and have it off, it’s best to check to make sure you have the correct amount of material so you’re getting traction on the grooves of the belt.”


A good time to evaluate belt wear is when your vehicle is in the shop having the water pump, alternator or other component repaired, especially if the vehicle is up in age. The average price for a Gates EPDM belt is $63, while a new belt and labor can run $80 or $90.

McGarity says as little as 5 percent of material wear can cause loss of tension, affecting the overall performance of components and lead to failure. Be sure to follow your operator’s manual for off-road equipment. John Deere recommends checking belt tension every 50 hours.

The easiest way to check for material loss is to use a gauge that fits between the ribs of the belt. Manufacturers Gates and Goodyear offer such hand-held devices that can be used with the belt on or off the engine.

The Gates Belt Wear Gauge has a “pin” or strip of plastic that sits above the ribs on a good belt. A finger hole at the end of the gauge enables the user to place the pin into a straight section of the belt and feel if it’s above or below the rib. The gauge can also be used to check individual ribs. Changes in depth indicate misalignment or other problems.

Gates also offers a free PIC Gauge app that takes a picture of the grooves and evaluates the belt – green is good.

Goodyear’s GatorGauge by Veyance Technologies offers three ways to inspect belts for wear. The first method works much like the Gates gauge. At the lower right are four small pins that fit into the grooves of the belt. Light between the gauge and the valley of the belt indicates the belt is in good condition. No light means the belt is worn and replacement is recommended.

A 2-inch window in the GatorGauge is designed for measuring rib wear. If two or more cracks appear in the window, it might be time to replace the belt. Other signs of wear include two cracks side by side in the same rib, belt chunking and cracks along the width of the belt.

A third measure of belt wear uses the slotted thickness indicator at

the top left of the GatorGauge. If the belt slides into the slot, it’s time for replacement.


Another way to tell if your belt needs replacing is visual inspection. Larry Gorski, a technician with Mid-State International Trucks of Wisconsin in Wausau, Wis., says he looks for pieces of missing rubber and abrasion. “If it gets off the pulley it will fray one of the edges,” he says.

Misalignment typically indicates internal components of the tensioner have failed and the assembly needs to be replaced.

Belt tensioning systems are most often used on vehicles with a single serpentine belt. Since 2004, manufacturers have been designing self-tensioning EPDM belts for select vehicles.

Stretch Fit (Gates) and Stretch Belts (Goodyear) maintain constant belt tension without a mechanical tensioner. Tensile cord inside the EPDM belt is designed to elongate and stretch. Once installed, the belt recovers its shape to maintain proper tension. Self-tensioning belts are slightly shorter than standard EPDM belts and cannot be interchanged. Self-tensioning belts also should not be reused. 


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