Inawise Tyre Pressure Monitor: Product Test
The importance of knowing your tyre pressures and temperatures on a big caravan trip cannot be overstated. If you are moving between smooth and rough bitumen, and graded to heavily corrugated, unsealed roads, you should be taking time to adjust the pressures accordingly on both your caravan and tow vehicle. Sure, it’s time consuming, but not as much as stopping to change a tyre or repair the things that will invariably break if you don’t.
The problem is that there is no hard and fast rule about how low you should go with your pressures, as this will depend on the weight of your rig, the size and type of your tyres, the severity of the corrugations and the ambient temperature. As a rough rule of thumb, you can drop the tyres on a tandem-axle caravan to 25-28psi for rough, unsealed roads and to around 30-34psi on single-axle vans – but always drive with caution.
But on bitumen on a hot day, low pressures like these can cause the tyre to overheat and fail. Conversely, on bitumen, some of the chunky offroad tyres fitted quite unnecessarily to caravans will overheat if you travel at high speed due to tread movement, even when they’re correctly inflated.
The problem with a caravan is that you may get no warning of these problems unless you can monitor all your tyre pressures and their temperatures while you are driving, and this is where tyre pressure monitoring systems (TPMS) are invaluable.
UNIQUE SYSTEM
There are several of these systems on the market, but we have recently put the US-developed and manufactured Inawise TPMS to the test over nearly 8000km. It most closely resembles the factory-fitted systems currently being offered on high-end cars and 4WDs.
While other systems use pressure sensors mounted in the tyre valve caps, Inawise uniquely locates its sensor/transmitter modules inside the tyre itself at the base of the valve.
Information on the tyre’s pressure and internal temperature is then transmitted wirelessly via a small antenna attached magnetically under your tow vehicle to a ‘key’ corresponding to that specific sensor that is located inside a coloured display. This can sit on your dashboard, or can be attached to your windscreen via a supplied suction mount.
The Inawise system initially was developed for the US trucking industry and the TPMS-203 model we reviewed can monitor up to 12 tyres simultaneously, making it ideal for large caravans.
On our Land Rover Discovery/Coronet XT-2 rig, we had it set to monitor all eight road wheels, plus two spare wheels for the tow car and van.
The head unit continually cycles through the pressures one row at a time, showing first the tow car, then the caravan and finally the spare wheels in succession, while you can manually check on each row at any time.
You can also toggle between tyre pressure and temperature monitoring.
The TPMS-203 is pre-set for vehicles that run a recommended cold tyre inflation pressure ranging from 26psi to 66psi. After adjusting your tyres to the desired normal cold pressure you ‘set’ the system, which will then give you an audible and visual alarm if the tyre drops 20 per cent below or 30 per cent above the reference pressure. If you drop your pressures for offroad travel, you simply reset the base pressure on the head unit and it will re-calibrate these alarms.
Apart from its smart ‘original equipment’ look, the other main advantage of the Inawise system over others we have tried is, when travelling offroad, the sensors are not vulnerable to rocks and other peripheral damage like external valve-cap style sensors.
The only important thing to note is the valves need to be installed by someone who is either experienced with them or is very good at reading instructions as, otherwise, they can work loose.
We found this out in Port Douglas, Qld, when we took the Discovery in for a wheel balance to find that one wheel sensor had not been correctly fitted and was swirling around inside a front tyre.
The good news is that, if the sensor does dislodge, it has no effect on the performance of the tyre valve and we lost no pressure.
Our only other issue with the Inawise is that the curved, glossy black head unit creates a lot of reflection, but this could be solved simply by fitting a matte/non-reflective screen similar to those used on computers and mobile phones.
The Inawise TPMS-203-8 retails for $660 but you need to allow the cost of fitting the sensor valves to your wheels on top of this.
If you only want the system for your tow car or caravan, you could choose the TPMS-201-D which costs $319 for four sensors or $374 for five, including your spare wheel, or the TPMS-4WD equivalent costing $418 and $473 respectively.
The full feature appeared in Caravan World #544 December 2015. Subscribe today for the latest caravan reviews and news every month!