Future fleet and manufacturer wheel and tyre choices could be influenced by the introduction of the Worldwide harmonised Light Vehicles Test Procedure (WLTP), says Kwik Fit.

Recent years have seen manufacturers fit larger wheels to cars, which has a detrimental effect on CO2 emissions and fuel economy.

Additionally, fleet demand for sports utility vehicles (SUVs) has also increased but, as they are typically heavier and equipped with larger wheels and tyres than hatchbacks and saloons, that trend might reverse, says Kwik Fit.

WLTP takes into account all available options thus making variation in CO2 levels - and therefore company car benefit-in-kind tax rates and all other motoring-related taxes - vast and significantly more visible.

Andy Fern, GB fleet sales director at Kwik Fit, said: “If vehicle CO2 figures have not been influential in the compilation of company car policies to date they are now critical with the arrival of WLTP.

“In the short-term it has essentially created increased uncertainty for the fleet market, at a time when there’s already confusion with regards to the long-term future of diesel vehicles and the migration towards hybrid and electric models."

The proliferation of tyre makes, sizes and types has rapidly expanded in the last two decades. Tyre choice has increased by around 10% per year as vehicle manufacturers have chosen to fit bespoke tyres to their new vehicles.

In 1997, 19 tyre sizes accounted for up to 90% of company car tyre fitments. Today 120 tyre sizes account for 90% of fitment with the remaining 10% comprising a staggering 1,030 sizes.

Fern said: “Wheel rim size and width of a tyre have a direct correlation on a vehicle’s rolling resistance and therefore CO2 emissions. As a result, we may see vehicle manufacturers end the trend for larger wheels, or company car drivers may think twice about ticking the larger rim size option when specifying a vehicle as it will ultimately hit them in the pocket.”

He added: “We have seen the migration of company car drivers towards choosing SUVs in recent years and significantly higher WLTP-based emission figures that widen the CO2 gap with hatchbacks and saloons may put an end to that trend.”

The Government has said that it will retain the ‘old’ New European Driving Cycle (NEDC) vehicle testing procedure for tax purposes until April 2020.

However, during the current ‘transitional period’ vehicles tested to WLTP protocols are ‘converted’ into a so-called NEDC-correlated value using a European Commission-produced mathematical tool that strips out the influence of optional extras from the CO2 calculation.

It had been anticipated by the motor industry that NEDC-correlated figures would be tax neutral, but the reality has proved to be somewhat different. Figures from manufacturers that have published information to date suggest an average CO2 increase of around 10% or 10-15g/km.

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