Thumping tires

John Baxter is senior associate editor of Commercial Carrier Journal. E-mail
[email protected].

There’s often a big difference between ideal situations and the “real world.” One of the best examples is checking tire pressure. As you know, DOT regs require drivers to gauge tires as part of a pre-trip inspection and every three hours while on the road. Word on the roads is that, at many fleets, it just doesn’t happen.

Joseph Cummins is a former small fleet owner and driver who has long been bothered by this problem. He has worked hard to develop a well-engineered tire-beating instrument to help.

Cummins still advocates precision, believing drivers should gauge tires daily before starting out. But his impression is that there’s almost no chance of getting a driver to stop and check tires with a gauge at rest stops. “Tire manufacturers, safety experts and organizations preach the use of an air gauge as the only reliable way to determine if tires are properly inflated,” Cummins says.

“While this is logical, the concept is full of holes,” he says. “What driver is going to take the time to use an air gauge, whether accurately calibrated or not, that requires at least 10 minutes of precious time, which means less miles and less pay? The answer, sadly, is few to none.”

Cummins also argues that, given the highly variable pressure change that occurs as the tire heats up, the driver has a difficult time determining that a tire has lost, say, 8 psi from its proper inflation level even with a gauge.

The goal is to determine that a tire pressurized to 100-psi cold and checked before starting out has retained at least the equivalent of 80-psi cold pressure later in the day. Cummins’ research has shown most experts believe this is likely to prevent a catastrophic failure.

So Cummins developed a device called “Accu-Thump,” which will allow most drivers, after a little practice, to meet the fundamental goal. The biggest problem with most devices is that the footprint produced against the rubber changes when the angle of attack changes, Cummins says. He discovered that it’s this footprint that determines most of the sound and feel the driver gets when he whacks the tire.

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Cummins also discovered that the user needs a device that’s heavy enough at the business end to significantly flex the tire. But unless the weight is concentrated at the outer end, the device can be so heavy the driver will experience fatigue and won’t hit the tire with consistent force.

The patented device has a bulbous outer end with an edge that consists of a 90-plus-degree convex curve with a constant radius. The driver can change the angle of the tool or the contact point on the tire considerably and still have exactly the same footprint contact the tire. The device is also built with a handle much narrower and smaller than the head so as much of the weight as possible will be concentrated in the head. It only weighs 3.5 or 4.5 pounds, depending upon which version you get. The result is a consistent sound and feel when the Accu-Thump bounces off the tire – if the pressure is consistent. The sound is very different, and there’s much less bounce, when the pressure has dropped.

Take a look at Accu-Thump at It’s a less-than-perfect solution, as Cummins himself admits. But in a less than perfect world, it has to be better than drivers not rechecking their tires at all.