We recommend tyre pressure monitoring systems that score 90% or more for accuracy.

The overall score is made up of accuracy (70%), display (15%) and ease of removing the sensor to adjust tyre pressures (15%).

Tyre pressures were set to 35 psi using a calibrated pressure gauge and readings were taken for each tyre from the device's in-car display. The results were averaged and scored on the difference from the reference reading.

Our experts assessed the display for quality and clarity of readings.

Our experts removed the sensors from the tyres to evaluate how easy it is to adjust tyre pressure if required.

This measures how fine an increment you can adjust the alert ranges in – the smaller the increment, the higher the score.

'Tested model' means you ought to be able to find this unit in stores and online. Discontinued models may still be available second-hand.

The recommended retail price at the time of testing. You may be able to find better deals by shopping around.

What is the maximum distance the head unit can pick up a signal from the sensors? This is important if you're towing a trailer or caravan.

Where the tyre pressure monitoring system was assembled.

The size of the increments of pressure adjustment

All the products in this test come supplied with four sensors but some allow for extra sensors to be added to the system for use with caravans and trailers. 

The range of pressures at which the sensors are claimed to be accurate. Be sure to choose the product that's suitable for your application. Four-wheel drives may use pressures below 20 psi, regular road cars usually somewhere between 25 and 40 psi, and some caravans and trailers require over 50 psi.

The recommended operating temperature range of the sensors. 

The type of replacement battery required for each sensor.

A list of the items supplied with each system tested.

Does the unit alert you to excessively high or low tyre pressure?

How the unit indicates there's a problem.

Does the unit alert you to a failed or missing sensor?

Whether you can adjust the upper and lower pressure limits.

Does the unit notify you of high tyre temperatures?

Does the unit warn you when one or more sensor batteries are running low?

Detects a fast leak and sends an alert to the display unit so you can stop safely before the tyre becomes severely deflated.