Optimizing tire inflation pressure in the summer

Optimizing truck tire inflation pressure in the summer

tires-wheels-column

The sweltering summer season is when the nation’s highways seem to have more tire debris littering the roads. These road alligators can be dangerous. Drivers slaloming to avoid the alligators can cause accidents. If you do run over this road debris, the combination of steel and rubber can damage your vehicle and sometimes even fly up and hit another vehicle.

Interestingly, the motoring public generally believes that these are primarily bad retreads, giving the retread industry a negative reputation. In reality, these road alligators appear on the road mostly due to tires that were underinflated. Heavy loads and high speeds combining with underinflated tires is the worst possible scenario for commercial truck tires. It may be a new tire or it may be a retread, but any significantly underinflated tire will probably fail. The excessive heat being generated by an underinflated tire due to the increased flexing of the tire sidewalls in combination with the longer footprint (more rubber on the road) leads to the rubber compounds failing, and eventually, road alligators.

Industry surveys have shown the same results when it comes to tire pressures—steer tires have the best tire pressure of all wheel positions. Drivers actually check their steer tire pressure, and they feel pulling and a shimmy from low pressure steer tires. Low steer tires are a serious safety issue. Drive tires are next in the inflation pecking order. Drivers will not check drive tire pressures quite as frequently as steer tires, but they do get checked.

Outside duals typically have better pressures compared to the inside duals. It takes more effort to bend down and reach the pressure gauge inside the wheel hand holes to measure those inside dual tires. In addition, you usually get dirty and it’s not good for the back. It is also interesting to note that the driver side tires are statistically better for proper tire pressure. More effort is required to walk around the vehicle and check the right side tires.

Looking for more insight on tires and wheels? Click here to read through Al Cohn’s archive of columns.

Trailer tires always have the poorest inflation pressure for several reasons. Maintenance may not see a trailer for weeks, months or even a year. Drivers just don’t spend the time and effort required to check trailer tire pressures. The most interesting statistic from trailer tire inflation pressure surveys is that the right rear inside trailer is usually the lowest tire pressure of all 18 wheel positions. Drivers seldom make it to that tire wheel position.

Driver education regarding accuracy of tire pressure gauges should be mandatory training. Drivers who purchase the “tire thumper” at their local truck stop are completely misinformed. Tire thumpers may reveal a tire with 5 or 10 PSI, but it is impossible to distinguish between a tire with 70, 80, 90, 100 or 110 PSI. The stick pressure gauge is the most common tire pressure gauge used by drivers and technicians. The issue with stick gauges is their accuracy. Regardless of manufacturer, stick gauges are only accurate to plus-or-minus (+/-) 3 PSI brand new out of the box. Using a brand new pressure gauge may reveal a tire with actual 100 PSI to be 97 PSI, and the same tire with a second gauge may give an answer of 103 PSI. Dropping a gauge a few times on the hard concrete surface can change the accuracy very quickly to +/- 5 PSI. Over the years, visiting tire shops, going through the exercise of having 10 technicians all check the same tire with different pressure gauges will show a dramatic range of tire pressure readings.

Pressure gauges need to be checked for accuracy using a master gauge or air gauge certified station. If it is not accurate, the best solution is to throw it away. There are some stick gauges on the market which have a set screw on the bottom of the gauge which allows it to be calibrated.

It is important for fleets to work with their tire professional to determine the recommended tire pressure for steer, drive and trailer tires. Air pressure is based on the worst case load the tire will see in the real world. The tire companies all publish load/inflation tables that identify the proper tire pressure for a given load depending if the tire is being run as a single or dual. Keeping tires properly inflated will significantly reduce the road alligators and improve safety in the process.

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