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Tyre pressure

Correct tyre inflation pressure and where can I find it?

The tyre pressures specified for your vehicle are agreed between the vehicle manufacturer and the tyre producer. The recommended tyre pressures for your vehicle/tyre combination can be found in your vehicle handbook, inside the fuel filler flap or  on the driver's door post. 

Tyre pressure influences many important characteristics of the vehicle performance, such as: driving comfort, directional stability, cornering and braking grip, plus the general handling behaviour.

Driving with incorrect tyre pressure will have a negative influence on one or more of these important characteristics.  

How should tyre inflation pressure be checked?

Your tyres must be inflated to the pressure specified by the vehicle and tyre manufacturer. This normally varies depending on the load and service conditions.

The specified pressure always refers to the COLD tyre and must not be allowed to fall below this value. The pressure inside warm tyres will be higher due to the fact that driving causes heat build up. So never reduce the pressure inside warm tyres. because when they have cooled down their pressure could fall to below the minimum tyre pressure.

The tyre pressure (including the spare if you have one) should be checked and adjusted every 14 days. Especially important is to check and adjust your tyre pressures before going on a long journey or on holiday, where the additional load may require the tyre pressures to be increased according to the specification.

The effect of overinflation

Driving on overinflated tyres will have a negative impact on:

  • driving comfort
  • directional stability
  • Vehicle handling behaviour, especially when cornering at speed
  • Irregular wear

Keep to the specified pressures recommended by the vehicle and tyre manufacturer.

The effect of underinflation

Driving on underinflated tyres has a negative impact on:

  • steering response
  • directional stability
  • driving safety (tyres can dislodge from the rim when cornering)
  • economy (higher fuel consumption, lower mileage)
  • tyre durability
  • irregular wear

SAFETY WARNING - Underinflation can lead to the inside of the tyre being damaged. This can result in tyre failure or even a blowout. Hidden tyre damages are not rectified by adjusting the tyre pressure.

Tyre Pressure Monitoring Systems (TPMS)

A Tyre Pressure Monitoring System (TPMS) must be installed in all new cars (category M1) from November 1st, 2014 onwards in Europe. The Tyre Pressure Monitoring Systems can be based on different concepts and sensors. There are essentially 2 main types of TPMS system:

Direct systems - pressure sensors integrated with the valve or attached to the rim or inside of the tyre.

Indirect systems - no pressure sensor fitted to the tyre/rim. Pressure differences are measured "indirectly" via for example tyre rolling circumference changes.

Car manufacturers may opt either for direct or for indirect systems.

Fitment and maintenance of TPMS systems should be left to the tyre specialists.

Nitrogen in Tyres

Nitrogen is sometimes offered as an alternative to air for tyre inflation.

Nitrogen is an inert (non-flammable) gas – basically, nothing more than dry air with oxygen removed.

Air contains about 78% nitrogen. Because of nitrogen’s inert properties, it is often used in highly specialized tyre service applications and/or demanding environments such as aircraft and mining applications. Nitrogen is also often used in motor racing.

For normal tyre service applications, nitrogen tyre inflation is not required. However, nitrogen tyre inflation does not harm tyres and may marginally contribute to reductions in tyre inflation loss by permeation. Nevertheless, nitrogen will not prevent any tyre inflation loss caused by punctures, tyre/rim interface (bead) leaks, valve leaks, valve/rim interface leaks, wheel leaks, etc.

Whether inflated with air or nitrogen, regular tyre inflation pressure maintenance remains critical and necessary. Use of nitrogen alone is not a replacement for regular tyre inflation pressure maintenance.