We all know that the tyres on our vehicles need pressurised air to ensure safe and confident operation. But what if the tyres are under-inflated or running really low in pressure?

So, did you spot the difference in the photo above? One tyre is actually 10 PSI (or 70 kPa) lower than the recommended pressure.

Generally, car tyres have an operating tyre pressure of 33 PSI or 230 kPa. A slight difference is not a big deal, for example, a variation of one to three PSI (or 7- 21 kPa) but lower than 25% of the recommended (or 25 PSI/175 kPa) is unsafe and in fact, will be noticeable at the steering wheel. Here are the reasons why you should not continue driving if your tyres are under-inflated.

The tyre pressure information can usually be found at body section of the driver’s door, next to the seat

1. Under-inflated tyres affect safe handling

This is the first sign of under-inflated tyres. The vehicle will tend to deviate to the side where the tyre with much lower pressure is. Without air pressure holding and supporting the sidewall of the tyre, steering the vehicle becomes incredibly difficult.

The tyre, now being compressed by the weight of the vehicle, struggle to provide sufficient grip for drive, steering and braking. If your steering feels heavier, or more effort is required to rotate it, drive carefully to the nearest petrol station to fill up the tyres if possible, as there is a high chance of an under-inflated tyre or even punctured.

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2. Under-inflated tyres can cause a blowout

As the weight of the vehicle compresses the tyre due to under-inflation, heat builds up at the sidewall. Driving at highway speeds will generate even more heat and this heat leads to tyre failure or blowout.

Example of a tyre blowout. Image: idrivesafely

A blowout happens without any warning and can cause a loss of control that leads to an unfortunate collision or accident.    

3. Under-inflated tyres consume more fuel

More energy is needed to move the tyre in every direction due to a greater increase in rolling resistance as a result of under-inflation. Acceleration will be more sluggish, which in turn will make the car consume more fuel.

The rubber valves do not hold tyre pressure for a long period. In fact, it is said that air pressure escapes at a rate of 1 PSI / 7 kPa per month, so always make it a habit to check the tyre pressures every two weeks.

In the comparison photo above, the tyre on left has lower pressure by 10 PSI / 70 kPa and this is not visible to our eyes, thus the more reason to have the habit of checking the tyre pressures regularly.

4. Under-inflated tyres wear out a lot faster

Under-inflated tyres also reduce the lifespan of the tyre, as lack of air pressure means the structural shape of the tyre is deformed, leading to a distorted tyre footprint.

Image: Goodyear Australia

As the tyre’s sidewall and shoulders now support the vehicle to an even bigger scale, the inner and outer edges of the tyre will wear faster. Wearing out (or disappearance) of the “blocky” tread is also an indication that your tyres are under-inflated. Over inflating the tyres are also a bad idea, as the ride will become harsh and again shortened the lifespan of the tyre through an increased wear at the centre.

What about the runflat tyres (RFT), where it will still provide mobility even with a total loss of air pressure? These are designed to be driven even without air pressure but only to the nearest tyre repair workshop. Learn more about RFTs here.  

Always make it a routine to check the tyre pressures in your car every two weeks, and don’t forget the fifth/spare tyre! Maintaining proper tyre pressure allows your vehicle to deliver the fuel economy, handling and safety it was designed to deliver.