According to the regulations,
all light duty vehicles built
after September 1, 2007 that fall
under the regulations
must be equipped with a system. Two types of monitoring systems are allowed.
use the anti lock brake system wheel
speed sensors to monitor differences
in tire rotational speeds.
A tire with low pressure has a smaller rolling radius and will rotate faster. Indirect systems can't monitor actual tire pressure.
They only compare tire rotating speeds.
most common system installed
on new vehicles. These systems
have a pressure sensor/transmitter
attached to each of the vehicle's wheels, where they sense actual tire pressure. This information is transmitted by radio
frequency to a receiver inside the vehicle, which monitors the system and activates warnings.
On many vehicles, it is
even possible to read tire pressures on driver information displays so you
don't have to leave your
vehicle to check tire pressures.
Tire pressure sensors
on direct systems may be strapped
to the wheel centre or they
may be part of the valve stem assembly.
If you see a large metal
valve stem that is held in place
by a nut (who is not your husband),
then you probably have a system
on your vehicle, but some of the new systems are using a replaceable rubber valve stem that looks very much like a
conventional valve stem. Many sensors are powered by a small battery that will last about 10 years, maybe.
Some sensors are powered by an internal crystal that excites itself due to road shock.
All these direct systems
work equally well but please
tell us if you have one on your vehicle
before you have any
tires changed or repaired, so we can notify the repair technician.
It is easy to damage a sensor when removing a tire, especially if the person is not aware it has a sensor on the wheel.
There are several manufacturers
of original equipment and aftermarket
tire pressure monitoring systems.
Beru systems are used
by Audi/Volkswagen, BMW, Land
Rover, Mercedes-Benz and Porsche.
Schrader make systems for Ford, Chrysler, GM and Nissan/Infiniti.
Lexus has used a system by Pacific.
Siemens is another provider of monitoring systems.
As usual, to make life
difficult and as you would expect,
even though several auto manufacturers
may use systems
from the same supplier, there are few similarities between manufacturers.
Valve stem attachments
are usually different. The shape
of the sensor differs so it will
fit different wheels.
The only thing all systems with valve stem sensors have in common is that they use a special nickel-plated valve core.
Install a regular brass valve core in one of these sensors and it will corrode and seize in the sensor.
Then you will have to replace the complete sensor the next time you want to add air.
Tire pressure monitoring
systems may seem like a good
However, they only warn
when a tire is getting dangerously
These warning systems
do not replace regularly checking
the tire pressures.
There are still some problems
with the systems too.
Living in a cold climate,
means there is a considerable
change in tire pressure between
a reasonably warm garage
and a frigid winter morning.
Many of the vehicles will
warn of low pressure because the drop in temperature lowers tire pressure.
This can happen every
morning, even though the tire
pressures are adjusted correctly.
The systems may not be perfect, but they do direct you to check the tires before tire pressure becomes critically low.In one case we encountered recently, an owner had attempted to extinguish the warning light by applying more and