WHY TYRE PRESSURES ARE IMPORTANT

The tyre is the only point of contact between the car and the road.  It is one of the most important components on the vehicle that contribute to your safety.  If the tyre is not correctly inflated it can affect handling, braking, steering, ride quality and fuel economy.

An under-inflated tyre requires more effort to roll, and will adversely affect the vehicles fuel economy.  An under-inflated tyre has more of a ‘bulge’ in the side wall, and this larger ‘bulge’ causes the tyre to flex more as it rotates, generating extra heat in the tyre material.  This extra heat could, if the tyre pressures are quite low, generate temperatures that will cause the tyre material to loose it’s structural properties, leading to a sudden blow-out.

An over-inflated tyre will have a more rigid and less flexible tyre sidewall.  This will lead to a harsher ride, increased tyre wear and a reduction in grip and vehicle control.

Tyre and vehicle manufacturers worked very hard during the development of your vehicle to find the right balance between grip, ride comfort and fuel economy.  We always recommend that you inflate your tyres to the manufacturers stated cold tyre pressures.

Our tyre pressure monitoring systems allow you to check in real-time the pressure and temperature of your tyres.  However, our tyre pressure monitoring systems do not replace the visual checks needed to ensure your tyres are in good condition.  We recommend that you conduct weekly checks on your tyres to assess if they have the following defects:

  • Wear close to or below the tyre’s wear indicators moulded into the tyre tread.  Use a tyre tread depth gauge for a more accurate reading.  Excessively worn tyres cannot cope with wet roads, increasing the chances for the tyre to aqua-plane on patches of standing water, leading to loss of vehicle control.  In addition you will be fined and receive points on your licence if you are stopped with excessively worn tyres.

 

  • Uneven wear of the tyre tread which indicates that the suspension and steering geometry is misaligned.  Misaligned suspension and steering geometry will rapidly increase tyre wear, and could affect vehicle handling, driver control and fuel economy.

 

  • Cracked side walls.  Old tyres eventually degrade as they are attacked by UV light, ozone and chemicals.  These small cracks weaken the tyre structure, and indicate tyre grip has been reduced.  Tyres with  cracks in the side wall must be replaced

 

  • Bulges, and splits in the sidewall. Hitting potholes and kerbs may not cause immediate damage to your tyre, but over time the impact can cause the material in your tyre to weaken and split.  If a bulge appears in your tyre sidewall this indicates that the inner structural fabric of the tyre has broken.  This tyre could burst at any moment.  Do not drive the vehicle with a tyre in this condition until a new tyre has been fitted.

EFFECT OF TEMPERATURE

Tyre pressure is determined by two factors. The volume of air in the tyre, and the temperature of the air.  If the air is heated it wants to take up more volume.  The air trapped inside the tyre cannot increase it’s volume, so instead the tyre pressure increases.  The opposite occurs when the air in the tyre is cooled.

Tyre and vehicle manufacturers allow for the normal heating and cooling of the tyres when specifying the recommended tyre pressures.

Vehicle handbook tyre pressures are specified for cold tyres. The tyres warm up during driving, due to the flexing of the tyre sidewall, and the extra heat causes the tyre pressure to increase by about 10% in normal service.  Tyre pressures should, therefore, be checked before they are heated by driving.

In winter, tyre pressures fall due to low ambient temperatures. Additional air will be required to bring them back up to manufacturers recommended pressure.

In summer, tyre pressures rise due to higher ambient temperatures. Carefully removing air from the tyre will be required to bring them back down to manufacturers recommended pressure.

Re-setting tyre pressures may need to occur more regularly on inter-continental road trips, where variations in ambient air temperatures can vary significantly in a short time period during the course of the trip.