TPMS stands for tyre pressure monitoring system. These systems have been fitted to all new vehicles for sale as of November 2014. TPMS can be direct or indirect. This article explains the difference between the two systems and provides some tips on using them.
As its name suggests, a direct TPMS measures tyre pressure directly and in real time. Each of the wheels is fitted with a pressure sensor, which is usually connected to the tyre valve. The sensor sends information to a receiver unit located in the vehicle. The driver is alerted if a loss of air pressure occurs. Direct TPMS are the most common and effective systems.
Accurate and responsive
Detects a faulty tyre
A constraint when changing tyres
Requires maintenance (seals need changing)
Limited lifespan (five to seven years)
Indirect TPMS: the easiest to maintain
Indirect TPMS do not measure tyre pressure but instead measure the rate of revolution of each of your car’s wheels. The system uses the ABS or ESP systems to check that wheels on the same axle are spinning at the same speed. If the rate of revolution differs (+/- 20%), you will be warned of the anomaly via a dashboard warning light.
Advantages of indirect TPMS
No special procedures required when changing a tyre
A simple and inexpensive system
No maintenance required
Disadvantages of indirect TPMS
Inaccurate and unresponsive (particularly for slow punctures)
Detects anomalies but without identifying which tyre has lost pressure
Direct or indirect TPMS – how to identify them
Direct TPMS are easy to identify if the sensor is incorporated into the valves. In this case, the external part of the valve is rigid and generally metallic.
Indirect TPMS use conventional valves made of flexible black plastic.
Some manufacturers only fit direct TPMS on their vehicles, they include: BMW, Fiat, Ford, Hyundai, Kia, Mercedes, Opel, Toyota.
Others only fit indirect systems, including Seat, and Skoda.
Some use both, depending on the model: e.g. Renault, Volkswagen, and Audi.