Fleet News

Tyres: Finding a balance between performance and long life

WITH any tyre, there is a balance to be found between performance, safety and long life.

But how can fleet decision-makers benchmark how many miles tyres should last when cars have different engine sizes, different drives (front, rear, 4x4 etc) and cover different routes?

Could they order drivers to achieve a certain mileage before their tyres are replaced?

How quickly can a bad driver shred a pair of tyres?

For fleets, this is the most contentious of all questions but in many cases, the response is 'How long is a piece of string?'

Roger Sanders, general manager, technical services, at Continental Tyre Group, understands more than most the vast range of criteria manufacturers have to address when building a safe fleet tyre.

He said: 'Specialist motoring magazines often conduct comparative tests but usually only on one or two different car models in any individual test. It cannot be assumed that if Brand A tyre comes out tops on one car model, it will automatically be the best on a different vehicle type. The most important requirement should always be one of safety and the only real way of ensuring tyre and vehicle compatibility is by fitting tyres which have vehicle manufacturer approval.'

Sanders believes that, as with any multi-functional product, if an improvement is made in one area it is likely to have an impact – often negative – on one or more of the other areas.

As a result, tyre designers are constantly balancing these to meet the changing needs of the market.

He added: 'The most demanding customer is arguably the vehicle manufacturer and in order for a tyre manufacturer to obtain approval of its products, the vehicle manufacturer will subject the tyre to a very arduous and thorough engineering approval test procedure.

'After all, the vehicle manufacturer wants every outsourced component to meet or exceed the image and performance of its marque.'

The approval programme can take anywhere between a few months to a few years, depending on how many performance improvements are required to ensure tyre and vehicle achieve a harmony.

But despite all the work on the track, drivers are the ones who make the biggest difference when it comes to assessing tyre life.

Sanders said: 'Research has shown that driving style can be the single difference between achieving 6,000 miles or 60,000 miles from a set of tyres.

'Studies of cars in fleets indicate that an average tyre mileage on an average mid-range car would be between 18,000 miles and 25,000 miles.

'However, with a total range of 7,000 to 40,000 miles, what value do average figures have?'

He believes it is also risky to assume that a driver achieving a low-tyre mileage is an aggressive driver and equally so to assume that one who achieves a high tyre mileage is a more sedate driver.

This is because journey routes, types of road used and ratio of city to open roads all have an impact on tyre wear.

Sanders said: 'The only reasonable accurate comparison is of two drivers using the same vehicle make and model and travelling the same routes at the same times of the year.

'It is a widespread view that generally a front wheel-drive vehicle achieves less overall mileage from its tyres than an equivalent rear-wheel drive model. As the trend has been towards front-wheel drive, principally to improve fuel consumption, tyre service life has reduced. Tyre manufacturers have tried to accommodate this and design in longer life, but not at the expense of road safety.'

So fleet managers beware. A tyre that achieves the highest mileage may not be the safest, nor may it be the best in terms of its influence on fuel consumption. Sanders said: 'A tyre that can save on fuel will usually reduce vehicle operating costs by bigger margins than one that lasts longer.'

Factors affecting tyre wear

  • Vehicle performance
  • Vehicle condition and maintenance
  • Weather conditions/climate
  • Geographical terrain
  • Road surface type
  • Ratio of use of fast straight roads (eg motorways) to undulating twisty/slow roads (eg urban roads/country lanes)
  • Tyre inflation pressure
  • Tyre loading
  • Type of tyre – eg summer tyre, winter tyre, 4x4 tyre etc
  • Driving style
    Source: Continental

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