What are the real reasons you need to lower your tyre pressures when you head off-road and go four wheel driving? In this article we discuss the two main reasons you need to lower your tyre pressures when four wheel driving.
If you are reading this article then you likely fall into one of two categories. 1- You enjoy four wheel driving and heading off-road. And, 2- You are looking to start heading off-road and are new to the world of four wheel driving and adventure. Which one are you?
Our vehicles are only in contact with the ground via a small patch of tread on each tyre, this is called the tyres footprint. We can change the footprint of each tyre by adjusting the air pressure in each tyre.
So what are the two main reason for lowering your tyre pressures when out four wheel driving? 1- TRACTION. and. 2- TYRE PROTECTION. Now lets dive a little bit deeper into these reasons.
1 – TRACTION.
This first reason, Traction, is what most people will have atleast a rough idea about. We need to have the most tread area incontact with the road surface as possible, as per the road, track conditions, environment and vehicle speed, that you are operating in and on. But what does that mean?
The reason we vary reason we vary tyre pressures, for traction, is that different surfaces have different grip levels (how easy it is for a tyre to spin or slide). Take, for example, a bitumen road in comparison to a wet and muddy track. The bitument road surface will almost always have better grip, (less likely to slip, spin and slide), than what a wet and muddy track will offer. Therefore, tyre pressures, on the bitumen, can be higher with less tread area, incontact with the road required for optimal traction. Whereas a wet and muddy track will need a larger tyre tread surface area to be in contact with the road surface, to stay on top, a bit like floating on top, of the mud to provide you with the optimal amount of traction.
An example of this senario is if you are to ride your push bike on a bitumen road and then ride that same bicycle through some mud, you will start to spin the back wheel of the bike in the mud because the wheel is basically cutting through the mud rather than “floating” on top of the mud.
Sand driving is another instance where your tyres need a larger “footprint” to stay on top of, float, that surface. Tyre pressure that is too high will mean that the chances of you getting bogged and stuck in the sand is greatly increased. Take it from me this is a very real possibility, having got myself bogged in the sandy bottomed Logans Creek Crossing on the Old Tele Track in Cape York, all due to inexperience with sand driving and tyre pressures that were way too high, as I drove through the sandy crossing the tyre didn’t have enough surface area to stay on top of the sand and basically dug into the sandy bottom, of the creek, rather than driving on top of the sandy bottomed crossing.
The one tale of caution that I do have in regards to lowering your tyre pressures is, the lower your tyre pressures, the lower your vehicle speed NEEDS to be, as high road speeds and low tyre pressures are a bad mix, and will eventually lead to tyre failure, more on that in a future article.
2 – TYRE PROTECTION.
The second reason for lowering your tyre pressures when four wheel driving is to protect your tyres. So how do lower tyre pressures protect your tyres?
Regardless of tyre size, a tyre with 45 p.s.i. of air pressure will have less of a footprint than a tyre with 10 p.s.i. of air pressure. The accompanying video also covers this topic, with a physical demonstration showing the different tyre footprints at various tyre pressures.
The tyres on your four wheel drive are effectively large balloons, and just like the birthday celebration staple, tyres are a rubber case filled with air and when poked by a relatively sharp object can puncture like one too.
Do a little demonstration for me, grap a couple of balloons and fill one with only a few breaths and tie it off. Now blow the other balloon up completely and tie it off as well. Next grab a pen and try to pop each balloon. What happened?……The balloon that was fully inflated popped really easy compared to the balloon that was only partially inflated, didn’t it?
Now imagine those balloons are the tyres on your four wheel drive and you drive over some rocks, or some sticks. If you have your tyre pressures at road pressures then the chances of obtaining a puncture, when you drive over the sharp obstacles, are far greater than if run over the exact same obstacles with a lower “off-road” pressure in your tyres.
The reason that the tyre, or even the balloon, with lower air pressure is more resistant to puncturing is because the tyre, or balloon, can flex, wrap and mould itself around the obstacle, that is trying to poke its way through. This practice helps your tyres live to see another challenge.
Just remember to return your four wheel drives tyres, back to their road going air pressures before you return to the bitumen, to avoid damaging your tyres carcass, but more on that in another article.
Getting out of the house and creating your own adventures can be extremely fun and rewarding and a four wheel drive can help you find even more places to visit, you kow the ones that are that bit harder to reach and access.
To make your time four wheel driving that bit more enjoyable and safer, getting to know how to use the tools and equipment you have available, yes I’m calling your tyres a tool, is an extremely important thing to know. Now you understand why you need to lower your tyre pressures when four wheel driving, so go on, get out there and put your new found knowledge into action.
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