As an adjunct to the Blog from Micko (Nov. 2011) this blog is an awareness for users on the TPMS Australia tyre pressure monitoring system.
Tyre Pressure Monitoring System
Having debated the advantages of having TPMS, I have bitten the bullet and invested in a system from TPMS Australia Pty Ltd.
I considered the advantages and disadvantages of both the internal and external mounted sensors and decided on the external type as I could purchase a system for $245 from Opposite Lock in
Adelaide. The sales assistant stated they had the units on special as they had excess stock left over from the recent Caravan and Camping show held last month.
The advantage of the external system is obviously the ease of installation. The TPMS sensors are a sealed unit, with a suggested battery life of 3 years, after which you need to replace the sensor at $50 each. They come with a locking ring secured by an allen key style screw. These should secure the units from accidental loss while driving, although theft may still be an issue.
One detriment to theft is that each sensor’s ID needs to be programmed into the display unit so theft without the security/serial number would render them to all intents and purposes useless for reuse. Each sensor in the kit is marked FL, FR, RL, RR and pre-programmed into the display unit so no setup other than ensuring they are attached to the corresponding wheel is required.
Other brand systems, such as the Tyre Dog (also stocked by Opposite Lock) use removable batteries and these may be subject to the possible ingress of water, say during a creek or
river crossing.
When considering the purchase, I spoke to my local tyre retailer for his input. He had no real knowledge of the various systems, other than mention that they need to be advised if internal sensors are installed to avoid accidental damage when removing a tyre from the rim.
The advantages of the internal sensor is a higher level of security and potentially the improved accuracy of data sent to the display unit. I will explain this further below.
One disadvantage of this type of sensor is that the tyre needs to be removed, both for initial installation and to replace the batteries or sensor, as they reach the end of their life.
Some internal sensors are sealed, with a battery life of 7 years, after which they would also need replacement.
Installation
The monitor unit has the ability to be powered by either two AA batteries, or connected to the vehicle’s cigarette style power socket via an included power cable. If batteries are installed, priority will be given to the external power supply. Batteries do not need to be removed.
Installation is quite simple. The monitor is turned on and the initial display is “blank” until the sensors are screwed onto each tyre valve, after which the sensor transmits it’s data to the monitor.
From this point, data is continuously cycled from one tyre to the next in sequence and both pressure and temperature are shown on the graphical diplay.
Results
Before installing the sensors, I checked the tyre pressure with my digital tyre gauge so that all tyres had the same pressure. This was done in the late afternoon/evening in an attempt to limit the sun’s impact on temperature variations. Tyre pressure by the gauge was set at 38psi.
The initial display showed a considerable difference in readings.
36 38
39 38
Recognising the gauge may not be accurate, the next morning I adjusted the left side front and rear pressures, having determined the gauge may be reading 0.5psi low.
The readings were checked and showed the same as the previous evening.
I adjusted the front left and rear left tyre pressures to read 38.5psi on my gauge and reattached the sensors. The monitor was left on during this period, a time lapse of approx ½ hour by the time I attached and detached the compressor and sensors.
Surprise, surprise.
I now had a reading as follows:-
39 36
37 36
I had not even touched the right side tyres.
Initial Conclusion
The external tyre sensors (at least) are not all that accurate and the pressures displayed are at best, approximate. No direct sunlight was being placed on any of the tyres during the adjustment period.
I have not even mentioned the temperature readings as even the sun on one sensor will have a marked impact on the result and they read all over the place anyway.
My reason for investing in a tyre pressure monitoring system was to reduce the potential impact of a deflating tyre on both the tyre itself and more importantly on vehicle control, if immediate awareness of a
puncture was noticed. This is not always immediately evident when travelling on unsealed roads and tracks, as I have previously experienced.
My confidence in the accuracy of accurate pressure monitoring has not been achieved from this particular system, however I am confident that a decrease in tyre pressure from a deflating tyre or the resulting increase in temperature will send an immediate alert to the monitor so that action by the driver can be achieved and therefore, my main reason for installing the TPMS, for a reasonable cost, has been met.
Note: all initial testing has been carried out with the vehicle stationary in my driveway.