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Adjusting tyre air-pressures: pros and cons

As our sole contact with the road, tyres are quiet achievers. So it pays to take notice of their condition. And central to their longevity and performance are their pressures.

Of course, what those pressures are vary according to where we drive. If we’re to make the right decisions, we need to understand the risks involved and what we can do to minimise them. 

LOW TYRE PRESSURES, THE BENEFITS AND RISKS

Four wheel drivers often lower tyre pressures off road or in challenging road conditions. 

Lower tyre pressures can increase contact with a track and hug obstacles that may otherwise puncture the tyre. 

But lower air-pressures also affect how we drive. Reduced steering, difficulties cornering and vibrations are common risks associated with running lower air pressures. Braking is also affected.

What’s more, because low air pressures change the shape of your tyres, tread wear on the tyres’ outside shoulders increases. And they tend to overheat, too, compounding the issue.

Low air pressures impact the vehicle, applying greater strain on your steering and suspension wheel bearings and chewing through the fuel. 

So avoid running low air pressures on good quality tarmac. And if conditions do call for low tyre pressures, minimise your load, prepare your turns and allow extra time for braking. 

HIGH TYRE PRESSURES, THE BENEFITS AND RISKS 

Running high air pressures on good quality roads support vehicles carrying heavy loads, but only if they’re within the tyre manufacturer’s recommended air-pressure or PSI range.

Any higher will impact your ride as they’re less able to absorb shock encountered roads. 

Excess air can also cause tyres to bulge resulting in uneven wear and less grip, impacting other parts of the vehicle. 

WHEN TO ADJUST

If your next adventure lays on a secluded stretch of sand, or at the end of a pot-holed or corrugated road, lower tyre pressures may be in order. 

So long, that is, your tyres are designed to operate under those conditions. 

These tyres are usually rated at LT tyres (light truck for a stronger side-wall rating) with an AT (all terrain) or MT (mud terrain) tread pattern.

Reputable manufacturers will advise on what air pressures to run off road or in rough road conditions. 

And if you plan to regularly tackle undulating terrain, keep abreast of your tyres’ air-pressures with a tyre pressure monitoring system, in case you forget to adjust them in new conditions. 

A good tyre pressure monitoring system will also indicate if your tyres are overheating.

tyre pressures pros cons
tyre pressures pros cons

MAINTAINING THE TREAD

Unsure of your tyres’ condition? Check out the tread wear indicator bars set between the tread grooves around the tyre. 

These square rubber nodes are 1.5mm deep, which is the minimum legal tread depth requirement. If these bars are flush with the tread surface on the road you’re breaking the law!

Tread wear indicator bars can help diagnose uneven wear caused by poor alignment and under or over inflated tyres.

DATING YOUR TYRES

No matter the condition of the tread, if the rubber is old, it’s less flexible and will crack increasing the risk of a blow out and failure. 

Thankfully, the date of your tyres’ manufacture is recorded in a serial number printed on the tyre’s side-wall.

Look for the 10 to 12 digit number preceded by DOT.

The final four digits identify the date, with the first two indicating the week of manufacture (say 09 indicating the 9th week, or 10 indicating the 10th), and the final two indicating the year.

Traditionally, six years was the rule of thumb for replacing a tyre on a trailer though modern compounds are improving. So refer to your tyre manufacturer for advice on replacement.

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