Trev’s Tips

Tyre Pressure monitoring systems

It’s not very often that a 4wd accessory can save us money and even if there was such an accessory they are generally not very popular.  Most of us choose accessories that either make our cars safer, more capable for touring off road or make our equipment better organised.

This months Trev’s tip is about tyre pressure monitoring systems (TPMS).  To the best of my knowledge no one in the club has one of these systems installed in their cars but a large percentage of the club has had to fork out $100’s for a new tyre at some stage after destroying them off road when perhaps one of these TPMS could have saved that.

So what is a TPMS?  TPMS have been available a few years now and some new luxury cars are fitted standard with them. They comprise of small sensors/transmitters mounted in a vehicles tryes that wirelessly send data to a programmable dash mounted receiver and will alert the driver if operating parameters move outside a preset range of temperature and pressure.

A TPMS does not stop punctures/leaks, but alerts you when tyres are operating outside normal temp and pressure parameters that you are able to program into the receiver.  If the tyre falls below the set pressure or above the set temperature an alarm will sound to alert the driver of the problem.  The idea is that if the driver is made aware of the faulty tyre early enough then it can be repaired before permanent damage is done by driving at pressures which are too low.

Many people think that when a tyre “blows” it happens very quickly.  While this may be the case it is more often that the tyre will blow after it has been driven flat for extended periods of time without notice from the driver.  To be fair with the current levels of comfort and technology such as stability control in cars today along with the rough roads we often drive over the driver can be hard pushed to notice a tyre which has dangerously low pressures.  Also with the low profile tyres on today's cars it can be hard to spot visually if the tyre is bludging due to low pressures.  A TPMS will alert the driver as soon as a pressure drop is detected thus minimising the risk of permanent tyre damage.

In speaking to my father recently who has one of these installed in his NP Pajero I was staggered to hear of some of the temperatures and pressures he had seen his tyres get to in normal touring operation.  

In one instances whilst travelling on a hot day with a loaded car and Jayco in tow on a gravel road at 95km/hr he observed the tyres gain 5psi (from 45 to 50psi) and reach a staggering 85⁰c.  To combat this he could have pumped the tyres up more to stop flex and thus reduce heat build up, but the tyres were already at their maximum recommended pressures.  He could have also reduced some of the weight in the car but I don’t think Mum was too keen on being left on the side of the road so his only option was to slow down.

Who knows what temperature the tyres would have gotten to if he’d been travelling on hot bitumen.

Interestingly none of the tyre manufactures were able to tell him if there was a maximum safe operating temperature for tyres.  85⁰c does seem a bit high though.  Had he pushed on driving without realising just how much stress the tyres were under a blow out would seem likely and at these speeds and with such loads on a gravel road the outcome could have been disastrous.

By being aware of the situation, slowing down and allowing the tyres to cool he has likely saved $100’s in damage to his tyres and perhaps $1000’s in repairs if an accident had occurred not to mention the elimination of potential safety hazards to the occupants.

TPMS are very easy to install, but do require you to break the bead on one side of each tyre.  This is to allow the sensor for each wheel to be attached to the valve on the inside of the rim.  A good operator could have the whole setup operational in 1.5hrs.  Alternatively a tyre dealer could fit the sensors in half this time but at a cost. 

There are number of different brands available for TPMS that vary in price and the number of tyres that they can monitor but to give you an idea, Repco stock one particular brand (airaware) for $300 that monitors 4 tyres. If it saves one tyre you will have just about recovered your costs.  Extra sensors can be purchased if you want to monitor other tyres such as the spare.  I have seen some systems advertised that will monitor 8 tyres if you want to keep the trailer tyres in check as well.

Other advantages of a TPMS.

· They can help to extend the overall life of your tyres because it becomes very easy to see if the tyres are not correctly inflated in normal everyday driving.  Being aware of any under inflation issues allows quick rectification of the situation and extended tyre life.

· The receiver unit can be used as an extra tyre pressure gauge.  This means when using your staun deflators to drop pressures to their preset amount (say 18psi), you can monitor each tyres deflation progress and if you want to stop at say 24psi for gravel road driving it is easy to see when this pressure has been achieved and halt deflation rather than having to do continuous manual checks.

· They allow you to see if your tyre pressures have altered once you have deflated them for sand driving.  This is something many of us regularly talk about.  After deflating our tyres to say 18psi for sand driving, shortly afterwards, a quick check will see pressures back up to 22 or 24psi.  It is not necessarily your bad driving causing you to bog down but the fact that your tyres are too hard even though you thought they were deflated to 18psi.  This increased pressure from the originally deflated 18psi is usually a result of extra flexing in the soft tyre causing heat build up and thus increased pressures, or a general rise in the temperature of the surface being driven over which transfers to the tyres causing a rise in temperature and pressure. 

Other options:

For around $10—$15 on ebay or some automotive stores you can buy pressure sensing valve caps.  These caps are purchased at a preset pressure which is not adjustable so make sure you get the right ones for your situation.  The cap will be green when the tyres are at or above the preset pressure, change to yellow if the pressure drops to 20% below the preset pressure and then to red if the pressure goes to 30% below the preset pressure.

Obviously they do not monitor temperature and you need to get out of your car to check them but as a quick visual indicator of a potential problem in everyday driving they are quite effective.

However with a system such as this, without constant monitoring in touring situations it is unlikely you will notice that one or more tyres has developed a leak over a short time interval meaning that the tyres could be driven on at low pressures till they suffer permanent damage so this system is definitely not as effective as a full TPMS.

 TPMS——   Worth serious consideration before your next big outback trip.

Till next time

Happy 4wding

Trevor

A dream without a plan is nothing more than a fantasy.