WHAT ARE THE DIFFERENCES BETWEEN A DIRECT AND AN INDIRECT SYSTEM?
A direct system measures the tyre pressure via a sensor integrated in the wheel. This information is wirelessly transferred to a control device in the vehicle. Various displays of individual vehicle manufacturers enable the driver to read the current pressure values permanently or to receive just a warning when the tyre pressure is too low. Such systems are very precise since they directly monitor the pressure for each wheel.
HOW DOES AN INDIRECT TPMS WORK?
In an indirect TPMS-System, the vehicle integrated ABS resp. traction sensors monitor individual wheel rotational speeds. Differences would occur if a pressure drop in the tires appears. In addition, pressure-dependent oscillations of the wheels are measured through advanced signal processing. A change will be considered a further indication of a loss of pressure.
WHAT ARE THE ADVANTAGES AND DISADVANTAGES OF THESE SYSTEMS?
A direct TPM-System allows for a very precise data collection and has additional functions like tyre position recognition, pressure loss detection when the vehicle is stationary and monitoring the tyre pressure of the spare wheel. A direct TPMS requires a significant extra effort and expenditure when changing tyres and during maintenance work. All tyres (summer, winter, spare) of a vehicle must be equipped with a properly working sensor.
An indirect TPMS is not as precise in its functionality since it neither measures the tyre pressure nor the tyre temperature. Also, it does not detect loss of pressure on the tyres when the vehicle is stationary.
WHAT EFFECTS HAVE TPM SYSTEMS ON MAINTENANCE AND SERVICE?
The use of TPMS when driving and maintaining a vehicle poses new challenges for the driver and workshops alike:
The vehicle owner will not be able to simply change a tyre by himself but will need the help of a specially qualified dealer in order to fit, calibrate and check the sensor of wheels with a direct TPMS. Due to the EU-wide introduction of this technology, specialist dealers will train their staff and invest in the required equipment.
CAN I FIT TYRES WITH DIRECT TPMS MYSELF?
Tyre mounting is a safety-relevant issue and requires expertise (check of a condition of the tire, use the correct tightening torque, ...). Therefore, we recommend this principle to only be carried out by a specialist dealer.
Direct TPM-Systems also bring the following new technical requirements:
The need for maintenance of the valve and the gaskets with every wheel removal to prevent wear of the sensor
For new tyres: new configuration of the sensors to the vehicle when new sensors (new sensor ID) are used or amending the wheel position of the sensors in order to ensure the clear communication between sensor and TPMS receiver
The battery level of the sensors must be checked when changing tyres
MY VEHICLE IS NOT EQUIPPED WITH A TPMS. DO I NOW NEED TO GET A TPMS FITTED?
Vehicles which are subject to the compulsory fitting of a TPMS will already be equipped with a direct or indirect TPMS by the vehicle manufacturer as otherwise the vehicle will not be given a type approval and/or certification in any of the EU member states.