Tyre Pressure

    Tyre Pressure

    Why is tyre pressure important?

    Tyres should be kept at the pressure recommended by the vehicle manufacturer at all times. Incorrect pressures can affect a vehicle’s handling, cause premature tyre wear and damage a tyre irreversibly.

    Motorists are encouraged to check tyre pressures regularly, at least once a month, and before every long journey, including the spare tyre where applicable.

    Tyre pressures should also be checked when the tyres are cold and before the vehicle travels long distances. As they warm, tyres increase in pressure which is a normal part of driving.

    The effects of under-inflated tyres

    Under-inflated tyres will suffer excessively from flexing and can become extra hot on a journey, which could lead to a dangerous blow-out. Low tyre pressure can also make the vehicle harder to control.

    Front tyres that are under-inflated can result in the vehicle under-steering, whilst rear tyres under-inflated can lead to over-steering, both situations are equally as dangerous.


    An under-inflated tyre doesn’t sit firmly on the road, as its edges deflect inward, lifting the centre of the tyre and therefore reducing the contact area. This affects braking performance and the tyre’s ability to clear surface water, which therefore increases the risk of aquaplaning.


    The extra loading on the edges of the tyre when under-inflated will cause rapid wear, reducing tyre life. In extreme cases, there could be wear and irreversible damage to the sidewall (C).


    The effects of over-inflated tyres

    Similar to under-inflated tyres, over-inflated tyres reduces the area of contact with the road, which can adversely affect vehicle handling and braking, leading to a higher risk of aquaplaning (B).

    Over-inflated tyres also increases wear in the centre of the tread, making the tyre more vulnerable to impact fracture or other casing failures.

    Finally, an over-inflated tyre doesn’t absorb road shocks as successfully, resulting in a much firmer and ultimately, uncomfortable journey.

    Tyre Pressure Monitoring Systems (TPMS)

    Tyre Pressure Monitoring Systems (TPMS) is a system fitted to a vehicle that will constantly monitor the pressures or pressure imbalances in the tyres. If pressures fall below a certain threshold, the system will then provide a warning light to the driver.

    Due to the importance of correct tyre pressures, TPMS is a very useful safety feature. However, TPMS should not be seen as a replacement for regular manual tyre safety checks.

    There are two types of TPMS systems are fitted on cars today:

    • Direct systems use the radio sensors mounted inside of each wheel to measure the tyre inflation pressures.
    • Indirect systems utilise the vehicle’s existing ABS sensors to measure and compare the rotational speeds of the tyres, which are affected by their pressures.

    Both types work with the vehicle’s main Electronic Control Unit (ECU) to alert the driver via dashboard warning lights to any pressure loss or variance issues.

    TPMS and the law

    Since November 2014, all new passenger vehicles sold in the EU must be equipped with TPMS.

    Furthermore, with effect from 1st January 2015, all vehicles fitted with TPMS when new will need to have a fully functioning system when undergoing their annual MOT test.

    Inoperative or faulty TPS systems will result in an MOT failure.

    TPMS and runflat tyres

    Runflat tyres are designed to provide a limited run-on period following a puncture. These types of tyres can be identified by the “RF” marking found on the tyre sidewall.

    Runflat tyres are only designed to run for a limited period, at a maximum speed of 50 mph with a limited load-carrying capacity.

    Due to the nature of runflat tyres, these should only ever be fitted to vehicles equipped with TPMS.

    TPMS servicing

    To ensure your TPMS system continues to operate properly and reduce the likelihood of an MOT failure, it may be necessary to have the system serviced occasionally.

    TPMS sensors are designed to last, however, after a certain period, the sensor’s internal battery will run out meaning a replacement is needed. In addition, sensors can become faulty or fail completely as a result of weather damage, corrosion or accidental damage caused when changing tyres. To ensure the sensor remains in good condition, many manufacturers recommend a replacement of the valve cap and core components every time a tyre is changed.

    When replacement TPMS sensors are fitted to your vehicle, your tyre fitter will need to program the new component to the car using specialist diagnostic equipment.

    If you need any further advice on tyre pressure, visit your local Maxxis dealer.

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