Fleet News

Tyres: tread carefully

TYRES can affect several aspects of a vehicle. They support the weight, transmit torque, provide traction and grip and contribute to acceleration.

Because of their integral role, fleet managers must ensure drivers regularly check tyres, even in between services. Michelin Tyres has produced a new guide outlining simple procedures fleet managers can pass on to drivers. Fleet News looks at some of the main points in the guide.

  • For a copy of the leaflet, call 0845 3661535. For general tyre information visit www.michelin.co.uk.

    Safe selection and use of tyres

    Selection and fitting

    As a general rule, fit only the tyre size and type recommeneded by the vehicle manufacturer. Except for the small number of cars that are designed with different tyre sizes, front and rear, the ideal fitment for optimum performance is always to have identical tyres all round. This principle becomes even more important at higher speeds. Consult tyre dealers for fitment, especially if in any doubt.

    Tyre pressures

    Drivers must check tyre pressures regularly, at least once a fortnight, and only when the tyres are cold. Tyres become warm when driving and the expanding air causes a slight increase in inflation. Make sure of the correct tyre pressures by using the information in the vehicle handbook or in the tyre manufacturer’s chart. Too little or too much air could adversely affect vehicle handling as well as the performance and durability of the tyres. Use an accurate pressure gauge and do not forget to check the pressure in the spare tyre.

    Valves

    Ensure that the tyre and wheel combination is fitted with the appropriate valve. Always use valve caps with a seal becase they retain the air within the tyres and give protection against ingress of dirt or grit.

    Tread wear

    Tyre tread wear should be checked regularly. Abnormal wear is often an indication of a mechanical defect on the vehicle, such as incorrect alignment, play in the steering mechanism or high spots on brake drums. In these cases the mechanical parts of the vehicle should be checked and rectified where necessary.

    Regular inspection will also help maintain tyres in good condition throughout their service life. Always ensure tyres conform to the legal requirements. Most car tyres have wear indicators in the grooves, which show when the tyre is worn to 1.6mm of remaining tread, the legal minimum limit. The appearance of these indicators level with the tyre’s surface means the tyre should be changed immediately.

    Tubeless and tubed

    Tubeless radials are very much the norm nowdays and it is important that they are fitted on the appropriate wheel rim. If tubes are used, ensure that they are the correct size for the tyre and rim. Michelin does not manufacturer tubes for car tyres with an aspect ratio (height of side wall in relation to tyre width) of 65% or less and does not recommend fitting tubes to any Michelin car tyre with an aspect ratio of less than 70%.

    General care

    In addition to maintenance of correct pressures, periodic visual checks for the following points can prevent unnecessary removal or even premature failure.

  • Stones or nails, if not removed when embedded into the tread, can work into the casing and cause damage and possible deflation.
  • Oil, fuel or paint can have a harmful effect on the rubber compound used in tyres. Oil can make the tread rubber swell, reducing the pattern grooves and affecting adhesion. Immediate removal with detergent and plenty of water is recommended.
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