Tyre Pressure Monitoring System (TPMS) for Your 4WD
Tyre Pressure Monitoring System (TPMS) for Your 4WD. In this post we explain what a TPMS is, how it works and whether or not they are worth it. If you want to read more about the OBD2 Australia TPMS setup in our 4WD then check it out here.
Why a Tyre Pressure Monitoring System (TPMS)?
What is a TPMS?
Tyre Pressure Monitoring Systems or a TPMS are exactly as the name suggests, a system that monitors the tyre pressures and temperatures in your vehicle. In the US and parts of Europe, tyre pressure monitoring systems are mandatory on any vehicle. This not however the cause here in Australia. An aftermarket tyre pressure monitoring system usually consists of a display unit and sensors that are fitted to each tyre. The display unit provides you the pressure and temperature readings of each tyre. These units allow you to set alarms so that you can be warned when your tyres go below or above a specific pressure. You can also set an alarm on the tyre temperatures as well. You are able to get tyre pressure monitoring systems with either internal or external tyre sensors. We discuss the differences of each type further below.
Why a TPMS for your 4WD?
As a tyre pressure monitoring system monitors the tyre pressures and temperatures of your 4WD, why is it a good idea to have one? Tyre pressures are so important for a number of different reasons. This includes extending your tyre life, improving ride comfort, reducing the risk of blowouts leading to tyre damage and overall road safety. Knowing your tyre pressures all the time, ensures your tyres are at the right pressure for the conditions you are driving in. Be it the ambient air temperature, track and road conditions, load in the rear of your 4WD, towing and the tow ball weight on your rear axle among other things. A tyre pressure monitoring system installed on your 4WD ensures you are continuously aware of the pressures in each tyre and how they are changing as you drive.
A tyre pressure monitoring system also provides you with real time temperature readings for each tyre. Why is this important? Well tyre temperatures are extremely important as it provides you with useful data. This data assist you in determining whether or not your cold tyre pressure was set correctly for the conditions you are driving. It will also provide you with early warning signs of any tyre pressure problems. From what we understand, we could be wrong here, you don’t really want your tyres to get above 70 degrees Celsius. Depending on your load, whether you are towing, the ambient air temperature and the track conditions, normal tyre temperatures should be somewhere below 50 degrees Celsius. Of course you will see tyre temperatures exceed 50 degrees in certain conditions but being aware of each tyre temperature allows you to make some important decisions before anything catastrophic happens.
Benefits of a TPMS for your 4WD
Having a tyre pressure monitoring system on your 4WD has a number of benefits as highlighted above, but here are a few of them in a bit more detail.
Early Warning from Pre-Set Alarms
The TPMS display unit allows you to set a number of different alarms. This being low pressure, high pressure and maximum temperature alarms. Low pressure alarms are great as you are able to get an early warning when you start to lose pressure in any of your tyres. Having an early warning allows you to pull over and deal with the issue before it becomes a major issue. Plugging a puncture is far cheaper and less painful than a blow out with a destroyed tyre and (or) rim. Having a constant display of every tyre’s pressure ensures that you are running the correct pressure for the conditions you are driving. How often do you air back up after a long days driving on the beach or a track and then check your pressure in the morning when your tyres have cooled down? Having a tyre pressure monitoring system will let you know that your tyre pressures the following day are actually a lot lower than you thought now that they have cooled down. Or how often do you actually check how your tyre pressures have moved from cold to hot when fully loaded to ensure you have set the correct cold pressure? Not very often I am sure.
Real Time Data
Being able to see how your tyre pressures are changing as you drive provides you with some extremely useful information. If you are towing a trailer and you notice that your tyre pressures in the rear are increasing a lot more than you expected, straight away you know that your initial cold pressures were too low. Some people talk about the 4PSI rule which can be used as a guide but not a source of truth. The 4PSI rule is fairly simple so is a good starting point to ensure you have the correct cold tyre pressure (of course ensuring you are running within your vehicle and tyre recommendations). Basically the idea is that if you notice that after an hour of driving that your tyre pressures have increased by more than 4PSI then your cold pressure was too low. For example, if you started at 38PSI and after an hour they are sitting at 48PSI, then you probably should increase your cold pressures to somewhere closer to 44PSI. This would be the same if the opposite occurred. That being, if your tyres only increased by say 2PSI then you would probably reduce your cold tyre pressures. This is only to be used as a guide ensuring you are within your vehicle and tyre maximum recommendations. In summary, you don’t want to be seeing large increases in tyre pressures, probably somewhere around 10% or so. If your tyre pressures are increasing more than they should this will cause tyre temperatures to also increase and potentially lead to failure.
If your cold tyre pressures are too low then:
- Your tyre pressures will increase by more than 10%
- Your tyre temperatures will increase higher than expected
Monitoring how your tyre pressures are changing as you drive ensure that you are setting the correct PSI for the load you are carrying. Any extra load on your axles will need a bit more pressure in your rear tyres. This is really useful information as it ensures you can rectify any potential problem quickly. Reducing the chances of a blowout, tyre and rim damage and the risk of an accident and injuring yourself, others and (or) your expensive gear. Having a tyre pressure monitoring system ensures you are kept constantly up to date on each tyre to ensure you are running the correct pressures for the conditions you are driving. For these reasons this is why we chose to fit a tyre pressure monitoring system (TPMS) in our 4WD setup. Ensuring we are constantly aware of each tyre pressure as well as be warned when we are losing pressure in any tyre. All of this ensures we are saving ourselves lots of money in repairs when something goes wrong, plus all the other benefits we discussed above.
Internal vs External Tyre Pressure Sensors
Now that you are aware of what a tyre pressure monitoring system is, let’s go through the two different types of aftermarket TPMS setups that you will commonly see sold in the Australian market. That being internal verse external tyre pressure sensors in a TPMS setup for your 4WD.
Type Will Depend on the Individual
The tyre pressure monitoring system we are using uses external tyre pressure sensors. These are fitted externally to the tyre by screwing a small circular sensor onto the tyre valve. Internal tyre pressure sensors are as the name suggests fitted inside the tyre replacing your valve in each tyre. We chose to go with external tyre pressure sensors for a couple of different reasons but this will really depend on the individual as there are advantages and disadvantages to both types of sensors. Here it will depend on what you are happy to sacrifice for the benefits of each. For us the sacrifice is the added time it takes when airing up and down, but we are happy to take a few extra minutes here for what we believe to be the benefits of the external tyre pressure sensor setup.
If you are purchasing one of these setups of the same brand, then the display units will be no different. Of course different brands and models will have different display units and features. So when comparing the OBD2 tyre pressure monitoring system (TPMS) that we have, they have both external and internal options. Here the features and functionality will depend on the brand chosen. Internal tyre pressure monitoring systems are usually slightly more expensive but again this will depend on the brand of choice.
Internal Sensors More Difficult to Install
Internal sensors require your tyres to be fully deflated and the sidewall of the tyre pushed in to fit each sensor. Internal tyre sensors replace your normal valve, so the installation time here is obviously longer and you might want to have this done by your local tyre shop. Although you could do this yourself if you know what you are doing and have the time. Here external tyre sensors are obviously easier and quicker to initially install as you simply screw these onto each tyre valve. The benefit here with internal tyre pressure sensors is once they are fitted, airing up and down is the same as normal, nothing changes. Having internal sensors will probably provide you more accurate tyre temperature readings as the sensor is within the tyre. External sensors from what we have found, only seem to provide temperatures a few degrees over the ambient air temperature. So internal tyre sensors, when it comes to airing up and down and providing temperature readings are the obvious winner here.
Rotating Tyres
If you are like us and rotate your wheels and tyres regularly, it is quick and easy to swap the external sensors around as your tyres are rotated around your 4WD. We remove the sensors before we have the tyres rotated by our local tyre shop so nothing gets damaged. We have our local tyre guys do the rotation as we also have steel rims so always get them re-balanced or else they are super uncomfortable to drive on. With internal tyre sensors, if you are buying a decent brand, you should be able to manually reprogram which sensor is in which tyre as they move around the 4WD. As a result you won’t need to remove them when rotating your tyres, just reprogram where the tyres have moved. If you don’t know where each tyre was rotated then you would need to deflate each tyre slightly, one at a time, to work out where each sensor is now located. If for some reason the system you purchased did not allow you to reprogram each sensor, then you would need to actually take each sensor out and move them. This would be a massive headache so make sure if you are buying internal sensors that they can be reprogrammed if rotated and stay away from any that do not allow you to do this. But remember, if you are rotating in your spare tyre, which you probably should, then you will need to add an internal sensors to this tyre.
Think About Your Spare Tyre
With each type of TPMS setup don’t forget about what will happen when you use the spare if you have a flat. With internal sensors you are probably not going to swap these from the flat to the spare until you have some time to do so. Here you will lose the benefit of the spare tyres’s reading on the display unit until the damaged tyre is fixed or the sensor is swapped. With external sensors these can be quickly swapped around.
Changing Batteries & Potential Loss or Damage
This again is an issue when the batteries in the tyre sensors need to be replaced. It is quicker and easier with the external sensors compared to the internal ones. However, this again will depend on the brand you are buying. Some sensors are sealed which means once the battery is dead the sensor needs to be completely replaced. The reason people buy sealed ones is due to the reduced risk of water and dust ingress to unsealed ones where you can replace the batteries. Another thing to be aware of with internal sensors, is that if you have an issue with a tyre and take it to someone to fix it, you will need to make them aware that you have internal sensors in your tyres. We have heard many stories of tyre shops damaging internal sensors when removing tyres from rims. They can easily be broken when removing a tyre from a rim, so this is likely to happen even if you do let the tyre shop know. With external sensors this shouldn’t be an issue as you can easily remove them before any work is done on a tyre.
One small benefit of internal sensors is they are unlikely to be lost from either theft or from falling off. External ones could fall off and be stolen, however we have found that they are not very noticeable and the locking nut does a great job in keeping them on tight. We have had no issues with any coming loose while driving some rough and corrugated roads for long periods of time. We do also air up and down quite regularly so are always keeping them nice and tight. The locking nut definitely makes the sensors far more difficult for someone to quickly try and remove.
External Sensors are the Winner
In our opinion, external sensors are the definite winner over internal ones. It is for the above differences we chose the external tyre sensors in our TPMS setup. We will take the hassle of an extra 2-5 minutes when airing up and down and the risk of losing them, for how easy it is to remove the sensors when you use your spare, faster to install and remove, no chance of damage when tyres are removed from the rims (as long as you remove them) and how much easier it is to replace the sensor batteries when required. Although we have found that the external sensors do not seem to provide accurate temperature readings (this may be different with other brands) where internal ones should be more accurate here. That being said, if we are running the correct pressures then temperatures shouldn’t be a big issue as they are directly correlated to one another.
Tyre Sensor Batteries
Sealed vs Unsealed Sensors
As briefly mentioned above, you are able to get TPMS setups with either sealed or unsealed sensors. Sealed sensors cannot have their batteries replaced and as a result need to be replaced when the battery dies. Unsealed sensors allow you to replace the batteries however there is more change of water and dust ingress. However we have yet to have any issues here and we have driven thousands of kilometres on dusty roads as well as been through a lot of water. Sealed sensors do usually have significantly longer battery lives compared to unsealed ones, so you shouldn’t be replacing sealed sensors very often.
Battery Life
One big disadvantage and or worry with tyre sensors is the battery life of the sensors. The shorter the battery life, the more of a nuisance they become if you need to be regularly changing batteries. Here we have had an issue with two of our sensors batteries dying within three months (these were advertised to last up to two years). From what we have worked out so far, we believe the issue we have had here is more due to the quality of battery used in the sensors from the supplier. These seem to be cheap, and we do not recognise the brand used. We have since replaced all batteries in every sensor with far better quality batteries to see if this results in a longer battery life. We are pretty sure we will see an improvement here, but will update this post over time to confirm if this is actually the case. Again depending on the brand you chose, you could expect better batteries than we received in the brand we bought.
Replacing Unsealed Sensor Batteries
Replacing the batteries in the sensors is fairly easy. For internal tyre sensors, you will of course need to deflate your tyres and push in your sidewall to do this. With our external sensors, to replace the battery, we simply have to remove the sensor from the tyre. Once removed, there is a cap on the back of the sensor that comes off easily. We then use the spanner tool to unscrew the battery from the sensor casing. The battery is a small watch type battery, a C1632 for size, that easily slides out and can then be replaced.
A TPMS Worth It?
So is a tyre pressure monitoring system worth it for your 4WD?
Most definitely yes in our opinion. We have learnt a great deal by having our tyre pressure monitoring system setup in our 4WD. Old dog experienced drivers and caravaners will roll their eyes at some of this as it is probably all basic information to them. However for us we have found it to be a great tool to ensure we have our tyre pressure set at the correct PSI all the time. Little things we have learnt about our 4WD setup such as different loads in different sections of the Cruiser have allowed us to ensure we get the right cold tyre pressures making sure we will get the best life out of tyres and reduce any costly damage when something goes wrong.
We decided to fit this setup to our 4WD just before we did our Simpson Desert and Outback Australia trip. We have seen enough videos of people getting punctures and only finding out when it is too late. Having our TPMS fitted in our 4WD gave us that extra comfort while we were driving, knowing that if anything went wrong we would have plenty of time to fix the issue. Not only fix the issue, but fix it while it was minor and before it became major. Fortunately for us, we ran the right tyre pressures for the conditions and did not have an issue with any blow outs that whole trip. Our tyres were in great condition which of course helped us here. But as we all know, tyre pressures have to be one of the most important factors when 4WD’ing. Having a tyre pressure monitoring system in your 4WD does make it a whole lot easier. We do now have the hassle of having to remove and refit the sensors every time we air down and back up again. But in the long run we think this is a small amount of pain for a hell of a lot of gain.
Check out our post that goes through our exact TPMS setup on our 4WD here. There are loads of options out there, so just get the right setup for your needs. If you are happy to spend a few more dollars then there are definitely better options out there.
If you would like to read any of our other posts on some of our gear, then check them out here. If you have any comments, questions or feedback then please comment below this post, we will respond to your questions and we do appreciate as much feedback as possible. To keep up to date on any future posts and become a part of the 4WD Adventurer community, then please subscribe to our Newsletter here. Follow us on Instagram, Facebook and YouTube to keep up to date on all our other content.
Thanks for reading legends.
The thoughts of Peter.
