Keeping a proper tire inflation pressure is a goal for every driver. When the proper air pressure is set, tire efficiency , fuel economy and durability are all maximized. Air in tires and supports car loads so depending on the specific load, the inflation pressure should be set accordingly.
For example, if a loaded tire is carrying 6,000 pounds when on the steer position, then the recommended tire inflation is 110 PSI for the common 295/75R22.5 low profile tire size. Load inflation manual describes the designed tire pressure made for given tire loads. These manuals can be found on each tire companies’ websites.
However, care must be exercised when reading these charts, since the recommended pressures have variance depending on whether the tires are being run as singles or duals.
Since it is totally difficult to change tire pressures every time the vehicle load changes, the recommended tire pressure at all times must be based on the worst case load scenario. Even if the average load may be significantly lower than the worst case load, it still is very recommended to set the pressure based on that worst case load scenario.
Load carrying vehicle drivers are typically worried about the frequency they should be checking tire pressures—and why tires lose so much air during the course of the year. Below are four reasons why tires lose air:
Gradual loss of air through the tire casing can result in a loss of 1 to 3 PSI per month, depending on the particular tire make and model. The chemical component of the manufacture of the tire can play a big role on this osmosis of air. The make and gauge of the tire innerliner compound also plays a significant role in osmosis. Losing 2 PSI per month does not seem like very much, but after 12 months the whole tire would be considered “flat” and should be removed from service. If a tire is found to be 20% under the fleet’s specification, the recommendation is to remove the tire from use, dismount and check exactly what is going on with the tire.
read more:http://www.automobileglobe.com/how-to-know-causes-of-tire-pressure-loss/