It could be argued that tyre pressures are more important to off-road enthusiasts than any other motorist, and while there are safety benefits (including improved emergency braking performance) as well as fuel efficiency and extended tyre life benefits to be had from maintaining correct tyre pressures for the average motorist, the world of tyre pressures is considerably more involved for those that like to leave the blacktop behind, and enjoy from time four-wheeling on a set of Open Country off-road tyres.
Unfortunately, the internet is awash with well-intentioned advice that’s often incorrect. How often have you ventured into a Facebook Group to read an overarching statement like ‘12psi is perfect for driving on sand,’ or that you ‘must air down to this tyre pressure for this particular track’?
To unravel the mystery around tyre pressures we sat down with Steve Burke, Tyre Technical Manager at Toyo Tires Australia to debunk the most egregious tyre pressure myths.
Placard pressures
For vehicles that haven’t deviated from the OE wheel and tyre configuration, your tyre placard is the first port of call when it comes to operating tyre pressures (that is, daily commuting and driving in normal conditions, on sealed roads). OE tyre pressures are set by engineers during the development of the vehicle and are designed to be the best compromise between optimal tyre performance, reasonable tyre wear and life, all while minimising in-cabin noise.
“Most placards will give you two or more tyre pressure recommendations - unladen and towing, for example - and they’re all fairly comfort-oriented, and all based on the OE wheel and tyre combination,” explains Steve. “However, when we change wheels and tyres or start adding extra weight through the addition of aftermarket vehicle accessories, these placard tyre pressures don’t really apply anymore.”
“Once we modify the vehicle or add weight it’s important to use the new vehicle weight to calculate the ideal tyre pressure, so you’ll want to head to a weighbridge and get individual axle weights, then contact our Tech Team - you don’t want to be guessing when it comes to tyre pressures, as accurate pressures directly relate to the quality of life of your tyre,” Steve adds.
Under-inflation
While lowering tyre pressures to optimise traction is commonplace when four-wheeling, leaving your tyres underinflated when commuting can have dire consequences.
“At the very least, you’ll notice slower steering response and extra tyre flex, because there isn’t enough pressure in the tyre to stop it pitching during corners,” begins Steve of the perils of underinflation. “Low tyre pressure will also have an adverse effect on your fuel economy,” he adds.
“Exploring some of the more serious side effects, you’ll notice poor cornering grip due to the tyre flex, which is especially dangerous in an emergency situation in the wet. Low pressures are also a great way to drastically reduce your tyre life - whether that's due to the uneven tyre wear you’ll experience, or due to the premature physical damage to the tyre caused by friction building up excess heat. Low tyre pressures are a premature tyre killer, and cost people a lot of money,” Steve explains.
Over-inflation
Acknowledging the issues associated with underinflated tyres, surely erring on the side of caution and running a little extra air should ensure you hassle-free motoring, right? Don’t be so sure.
Steve acknowledges that modern construction methods have made overinflation the lesser of two evils, and that many of the old wives’ tales about overinflation no longer ring true. But it isn’t a victimless crime. “Ride comfort is the obvious sacrifice,” explains Steve, alluding to the fact that as air pressure in the tyre increases, the tyre’s ability to insulate and absorb bumps in the road suffers.
“Grip is another one - overinflated tyres balloon out so that only the centre section of the tyre is making contact with the road, so you’re working with a smaller footprint in terms of tyre-to-road contact,” Steve continues, unearthing a pertinent safety concern associated with overinflated tyres.
“Thirdly, overinflated tyres can be more susceptible to damage, whether that’s foreign objects like sticks or rocks penetrating the tread face or sidewall, or structural damage happening beneath the skin that can result in tyre deformations such as sidewall bubbles.
Re-inflation
As well as maintaining optimised tyre pressures when commuting, Steve insists that remembering to air up isn’t exclusively for returning to the blacktop.
“Off-road tyre pressures should relate to speed, so whenever you’re doing a trail you’re correct to air down, but if you return to a fire trail or service road where you can increase to a moderate speed, it’s important to remember to re-inflate your tyres there, too! We see instances of tyre failure where people think that as long as the road is unsealed, that they should be running low pressures. A key indicator is damage around the bead,” explains Steve.
“Whenever someone rings me for tyre pressure advice we’ll take their axle weights, chat about their application and intended driving style and then I’ll give them three pressures - sealed road driving at highway speeds, unsealed dirt roads at a maximum of 80km/h and then sand (or equivalent terrain) at an average speed of 30km/h,” explains Steve of the way he and the Toyo Tires Technical Department calculate recommended tyre pressures.
If you’re looking for tailored tyre pressure advice for your Toyo Tires-equipped vehicle then you can contact Toyo Tires Australia directly, or consult with your local Toyo Tires Dealer.
