Trusting TPMS and garage inflators

Posted on July 11th, 2017 by Rob Marshall


With all new and many older cars fitted with Tyre Pressure Monitoring Systems (TPMS), owners are alerted virtually instantly of deviating pressures, which are so critical for dynamic safety and longer tyre life. Yet, checking tyre pressures may also highlight issues with air dispensers. Allow me to explain.

Recently, a journalist colleague swapped his cold weather Kumho tyres to the original-specification Bridgestone summer covers on his eight months-old Suzuki Baleno. Being a former competitive driver, he is aware of the affect that tyre pressures have on a car’s handling and requested that the tyre agent inflate them to 36psi all-round.

This led to a warning signal from the TPMS that could not be cancelled and, after several journeys, the car was inspected by a main dealership, which tested, reinflated and reset the system. Nothing was wrong. Two miles later, the dashboard pressure warning had re-appeared. This time, the car was taken to a local supermarket and the tyres verified as being inflated to 36psi all-round. This made no difference and our hero visited two separate filling stations to verify the pressures, bringing the total cost for air alone to £3.00.

In desperation, he booked the car into another main Suzuki dealership, which checked that not only was there nothing wrong with the factory TPMS but also reported that,  “The tyre pressures were all over the place”. It was explained that the sensitive TPMS on the Baleno has three settings, dependent on a trio of recommended air pressures, “Normal”, “Comfort” and another for heavy loads. The tyres were adjusted to a predetermined 36psi (front) and 32psi (rear), the ‘comfort’ setting. The action silenced the TPMS warning immediately.

Unsurprisingly, the journalist came away with two conclusions: not only were the forecourt tyre pumps (for which he had to pay) not calibrated correctly, which, considering their vital safety role, he judges as a disgrace, but he also recognised the importance of “reading the bloody handbook”!