Legislation passed by the European Parliament earlier this year will see all new cars sold in Europe from 2012 fitted as standard with a tyre pressure monitoring system (TPMS). However, fears are being expressed that one of the two TPMS technologies being made available to car companies may in fact put both motorists and the environment at risk.
The two systems, direct and indirect, approach the monitoring of a tyre’s pressure in different ways.
The tyre industry favours solutions such as the direct system which places a pressure sensor in each wheel and transmits reliable pressure measurement information back to the car data centre which then informs the driver immediately about the condition of its tyres.
The indirect system, favoured by some car companies and supported by OICA (Organisation International Constructeurs d’Automobiles), is a less expensive option, and measures the rotation rate of the tyres and compares one wheel against the others.
Some systems perform an analysis of the vibration characteristics using the ABS sensors. The car’s computer (ECU) analyses the data and works out if the tyre is changing diameter and the software interprets this as a loss of tyre pressure.
Critics say the delay in providing this information to the driver is opens up the possibility of a rapidly deflating tyre not being detected and the possibility of an accident.
The other crucial difference between the two systems is that the indirect version requires, when the tyre pressures are adjusted or a tyre changed, that the driver must – to make the system effective – re-calibrate the system. This relies heavily on the driver checking the tyre pressures with an accurate gauge, and in the optimum conditions when the rubber is cool, and then hitting the re-set button.
With tyre pressures ranking low down on the agenda of most drivers, the process is open to mistakes, critics argue.