TPMS, which stands for Tyre Pressure Monitoring Systems, have been around for many years, limited mainly to specialist vehicles. They are now however becoming more common as OE fitment on an increasing number of cars.
There are basically two types of TPMS:
- One that uses a sensor placed inside the tyre and wheel assembly (may be combined with valve or separate)
- One that uses the ABS system of the vehicle
With a sensor-based TPMS there is a pressure monitoring sensor fixed inside the wheel and tyre assembly, usually clamped to the wheel, that constantly monitors the internal pressure of the tyre. This information is relayed to a receiving unit on the vehicle body that is in turn connected to a processing unit in the vehicle’s electronics system that alerts a driver to a loss in tyre pressure.
Below is a selection of sensors available on the market today:
Picture shows a typical combination type TPMS sensor fitted to a rim
3 typical combination type TMPS sensors
Advantages of the combined TPMS sensor include accurate monitoring of the actual pressure inside the tyre and an immediate warning of a tyre deflation. Disadvantages include the fact that it is a more complex system (sensor, receiver plus processing unit) and it can be more difficult to fit the tyre due to the possibility of damage to the sensor if care is not taken.
This system uses the ABS of the vehicle to monitor the rotation speed of the individual wheels. If a deflation of a tyre occurs the resulting increase in wheel speed will trigger the TPMS and advise the driver accordingly.
Advantages of the ABS based system include the fact that the system uses technology and equipment that is already fitted to the vehicle. Also there are no sensors fitted inside the wheel/tyre assembly which makes the tyre fitting / removal process easier than with the sensor-based system.