Bendix Commercial Vehicle Systems LLC TX433VM User Manual
SmarTire Systems Inc.
Tire Monitoring System Reference Manual
6/20/2000 Page 40 of 56
This manual is under review by SmarTire – DO NOT ISSUE
Detecting Abnormal Tire Pressure
The MFD alerts the driver of abnormal tire pressure with a Pressure Deviation Alert or a Low
Pressure Warning.
Understanding Temperature Compensated Pressure Readings
An important feature of the SmarTire (MFD) system is that pressure alerts are initiated from a
temperature compensated pressure calculation rather than on the actual pressure read by the
sensor.
The reference pressure, or “cold pressure” is the air pressure inside the tire inflated at room
temperature (18º C) to the tire manufacturer’s recommendation. A tire that heats up, for example
to 28º C, will increase the air temperature inside the tire, resulting in increased air pressure. For
example a normal or “required” pressure at 18º C may be 34 PSI and a normal pressure at 28º C
may be 36 PSI. Both pressure readings are correct at their respective temperatures.
The amount of deviation from the required pressure (at any temperature) can be read by using the
Pressure Deviation mode of the MFD. If at any time you are uncertain that the Actual Pressure
reading on the display indicates the correct tire pressure, switch to the Pressure Deviation (+-)
readout. A blank display indicates that the reading on the display is the correct one. Any (+) or
(-) value indicates the tire pressure is incorrect by that value.
The Pressure Deviation Alert is temperature compensated.
The Low Pressure Warning is not temperature compensated.
The MFD alerts the driver of abnormal tire pressure with a Pressure Deviation Alert or a Low
Pressure Warning.
Understanding Temperature Compensated Pressure Readings
An important feature of the SmarTire (MFD) system is that pressure alerts are initiated from a
temperature compensated pressure calculation rather than on the actual pressure read by the
sensor.
The reference pressure, or “cold pressure” is the air pressure inside the tire inflated at room
temperature (18º C) to the tire manufacturer’s recommendation. A tire that heats up, for example
to 28º C, will increase the air temperature inside the tire, resulting in increased air pressure. For
example a normal or “required” pressure at 18º C may be 34 PSI and a normal pressure at 28º C
may be 36 PSI. Both pressure readings are correct at their respective temperatures.
The amount of deviation from the required pressure (at any temperature) can be read by using the
Pressure Deviation mode of the MFD. If at any time you are uncertain that the Actual Pressure
reading on the display indicates the correct tire pressure, switch to the Pressure Deviation (+-)
readout. A blank display indicates that the reading on the display is the correct one. Any (+) or
(-) value indicates the tire pressure is incorrect by that value.
The Pressure Deviation Alert is temperature compensated.
The Low Pressure Warning is not temperature compensated.