The problem with thumping a tire with a "Tire Billy" is that the average person can only tell if a tire is completely flat. When I present technical tire seminars, I give each participant a "Tire Billy" and ask them to hit several tires, then tell me which if any need air. When one tire has 100psi and the other has 40psi, almost everyone can tell. Hitting one generates a "ping," the other a "thud." When lining up tires ranging from 60psi to 90psi, surprisingly few people can detect which are under-inflated as the difference between them is too subtle. In service that range might be the difference between safety and catastrophe.
Hitting a tire with a stick to check pressure is about as silly as hitting the engine with a stick to check the oil. You must use a gauge.
You may be thinking that a tire will still reach its destination at 60psi, and in regards to many applications you would be right. Unfortunately, these moderately under-inflated tires may be a greater safety risk than flat tires. Continual use may severely weaken the sidewall cords but not to the point of breakage. Later when the tire is removed from service for repair and/or retread, the peril is concealed. The technician that re-inflates the tire could be in for a terrifying, even life-threatening surprise.
This condition is called a zipper rupture and is difficult to detect before the failure. It's called a zipper because the tips of the metal cords along the failure tend to look like the teeth of an open zipper. I've had some technicians tell me they heard a few pops prior to the blast. Others have witnessed tires that just blew with no warning.
RETURN ON INVESTMENT
Several years ago I was helping a large auto hauling fleet build and manage their tire program. The owner bought 900 high quality tire gauges and handed them out at driver meetings. A year later he could not understand why his tire expense and tire related breakdowns had not improved. I went to several of his yards to check pressures. As part of the test, when I found a low tire I would ask the driver to borrow his gauge just to be sure mine was accurate. After the first 40 drivers could not find their gauge, I had my answer. A $10 tire gauge will have a high return on investment but only if it's used religiously.
Jason Miller is the founder of The Tire Consultants, LLC. His book, "Selling by the Numbers," is available from Amazon.com.
TMC's Recommended Practices
Here's a sampling of what the new Recommended Practices from the Technology & Maintenance Council (TMC) have to say about tire maintenance.
RP 232A: Zipper Rupture Inspection procedures for truck and bus tires
The purpose of this Recommended Practice (RP) is to list inspection procedures for identifying potential circumferential ruptures (or zipper condition) on truck and bus tires (load range "F" and higher) and truck tires (load range "E"s and lower) of steel cord radial construction.
Service personnel should use caution when a vehicle equipped with steel cord radial truck/bus tires or light truck tires returns to its service facility and is suspected of operating with one or more tires underinflated and/or overload.
If this is the case, a trained tire technician must remove the valve core and completely deflate the tire before removing the tire/rim/wheel assembly from the vehicle. After the assembly is removed, the technician should dismount the tire frm the rim/wheel and conduct a complete visual and hands-on onspection of the tire.
• Punctures or other injuries
• Distortions or undulations (ripples or bulges) in the sidewall
• Cuts, snags, or chips that expose any body (ply) cords or steel wire
• Soft spots in the sidewall flex area
• Distortions or undulations (ripples or bulges)
• Protruding filaments (wire) indicating broken cords
• Any snapping, popping or crackling sounds
RP 235A: guidelines for tire inflation pressure maintenance
The purpose of this Recommended Practice is to demonstrate the importance of inflation pressure and its effect on tires and tire service life. It addresses all apsects of the relationship between inflation pressure and tires, and provides equipment users with a practical guide for better understanding the issues and costs that stem from failing to address this issue properly in everyday fleet operations. The RP applies to Class 2-8 commercial vehicles in light-, medium- and heavy-duty service.
This RP offers comprehensive guidelines on proper tire inflation pressure maintenance. It covers air pressure and its relevance to:
• irregular wear
• tire temperature
• steer axles
• dual assemblies
• automated systems
• determining correct pressure
• tire damage
For more information on TMC Recommended Practices, go to http://www.truckline.com/FEDERATION/
Be sure to check TMC's "Radial Tire & Disc Wheel Service Manual," part of the Tire and Wheel Essentials package, the complete information source on radial tire & disc wheel conditions and service. For more information, visit http://www.atabusinesssolutions.com
Visit http://tmc.truckline.com for more information about TMC.
(Recommended Practice excerpts used with permission of the Technology & Maintenance Council of the American Trucking Associations)
Think it is the same description as that used by vehicle safety compliance officers?
But there is no definition of an underinflated tire