Bendix Commercial Vehicle Systems SMARTIRE TPMS OPERATORS MANUAL - Manual (Page 10)

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1.3 HOW DOES THE SMARTIRE
™
TPMS SYSTEM WORK?
1. The SmarTire
™
Wireless Gateway receiver creates a wireless bubble around a vehicle
allowing various sensing technologies to seamlessly interact.
2. Tire sensors mounted on each wheel measure tire pressure and temperature every 12
seconds and wirelessly transmit tire data every three to five minutes.
3. Industrially designed for the rugged requirements of a commercial vehicle chassis, the
wireless gateway can monitor up to 20 wheel positions and is able to handle the most
complex commercial and off-highway vehicle configurations.
4. Real-time tire pressure and temperature information is available to the driver on demand
via the SmarTire
™
display. Ranging from a simple illuminated light to an easy to read and
simple to use interactive gauge that provides real-time tire status information, the
SmarTire
™
display will alert the driver to a low pressure or high temperature condition
before it becomes dangerous.
5. Trailer tires can also be monitored using a stand-alone system and/or trailer lamp.
6. The SmarTire
™
universal hand tool acts like an ‘electronic billy-club’ allowing
maintenance personnel to wirelessly ‘ping’ a tire to measure its real-time tire pressure.
The SmarTire
™
maintenance hand tool improves inflation accuracy and reduces
diagnostic time in order to keep every tire rolling cost effectively.
1.4 WHY IS TEMPERATURE MONITORING IMPORTANT?
THE PRESSURE TEMPERATURE RELATIONSHIP
Tire manufacturers specify that tire pressures should be checked and adjusted when a tire is
“cold”, but most people may not know why, or even what a “cold tire” is. The temperature of a tire
actually has a significant impact on its inflation pressure.
According to tire manufacturers, a tire is considered to be “cold” when its temperature is 65°F
(18°C). The inflation values provided by vehicle manufacturers, fleet maintenance personnel or
industry published load inflation tables are called ‘Cold Inflation Pressures’ (CIP) because they
represent the correct amount of pressure a tire should be inflated to when it is “cold”. The reason
that tires have cold inflation pressures set at specific temperatures is because a tire’s pressure
will change relative to its temperature.
Air naturally expands when heated and contracts when cooled. Inside a contained vessel such as
a tire, this expansion and contraction causes a change in contained air pressure. As a tire heats
up, its pressure will naturally increase and as it cools down, its pressure will naturally decrease.