Add a tyre pressure monitoring system to your car for R300 — with impressive results

MyBroadband tested an inexpensive tyre pressure monitoring system (TPMS) to determine if it is worth adding to an older car, and we were impressed with the results.

Most new luxury vehicles come with a built-in TPMS that warns the driver when a tyre is leaking or if a tyre’s pressure drops below a safe pressure.

It is an important safety feature, as a tyre with too little pressure negatively impacts fuel economy, tyre wear and can cause a tyre to burst.

Unfortunately, older or lower spec vehicles do not have this feature built-in.

TPMS add on kits are available from as little as R300 when ordered from China. They start at around R400 locally.

We tested a kit ordered from China that seems the same as most of the budget kits on the market.

The kit consists of the main screen module that shows the temperature and pressure of each tyre, four valve cap sensors, and anti-theft nuts.

The main module is battery-powered and can be charged by micro-USB or the included solar panel.

We stuck ours on the dash at the edge of the windscreen. It is sturdy, and we have not needed to charge it manually as the car gets a few hours of sunlight every day.

The module has alarms that you can set to minimum and maximum values for temperature and pressure.

If a tyre starts going flat, you are alerted with a loud beeping alarm.

The sensors screw onto the tyre valves instead of the valve caps. They include nuts that lock against them with a special wrench to prevent a thief from easily unscrewing them.

We were concerned about the accuracy of the sensors and decided to test them against an inflator gauge like you may find at a garage, against an analogue gauge, and an electronic handheld gauge.

We tested each of the sensors and the gauges ten times consecutively on the same tyre to see how consistent the measurements were.

We kept in mind that the tyre may lose a small amount of air every time a gauge is pressed against the valve.

The sensors perform well when it comes to consistency, with a maximum of 0.1 bar variation over the ten readings in the expected downward trajectory as some air is lost.

The graph below shows the variation of the different sensors over ten consecutive readings.

We then measured the accuracy of the sensors. We tested all the sensors in a series on one tyre and then in reverse sequence to get an accurate average.

The electronic and analogue gauges were up first, then left-front, right-front, left-rear and right-rear.

We then tested with the gauges again, followed by right-rear, left-rear, right-front, and left-front, ending with another test with the two gauges.

We tested four different pressures from the compressor, as different vehicles have different recommended tyre pressures.

The biggest surprise was the difference between the value stated by the inflator gauge and the readings from the two standalone meters.

The compressor gauge seems to be the least repeatable and generally shows a higher reading than the rest of the meters and sensors.

The inexpensive TPMS performed well, even though it was not as accurate as hoped.

The readings were generally around 0.1 to 0.2 bar lower than those on the standalone gauges we used, and those were usually lower than what was indicated by the inflator gauge.

The difference was larger at higher pressures, indicating that it may be a fixed percentage error than a fixed offset.

While this is not ideal, the sensors are accurate enough to indicate when a tyre has a slow puncture or is getting dangerously low.

Temperature also causes large fluctuations in pressure, and we have noticed changes of up to 0.4 bar in tyre pressures between a cold tyre and when the tyre is warm after a fast drive.

Considering the price, it is a no-brainer to add to a car without an integrated system. It is a cheap safeguard against a burst tyre, even if it is not perfectly accurate.

We have not had the sensors long enough to comment on their longevity. But even if they have to be replaced regularly, it is such a small cost relative to other vehicle parts and fuel.

The table below shows the average pressures recorded by the different sensors on a tyre pumped to various pressures. All pressures are given in bar.

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