Economy ratings on tyre labels don't reveal the full story on fuel efficiency, it has been claimed.
Research from road-based emissions specialist Emissions Analytics has found that, at certain speeds, tyres with a lower efficiency rating can perform as well as higher-rated tyres.
This means consumers opting for tyres with a higher efficiency rating may fail to notice any fuel savings, depending on the how they drive and the routes they take.
"Our test found that at mid-range speeds, F-rated tyres can perform as well as B-rated tyres." said Nick Molden, founder and chief executive of Emission Analytics. "Tyre efficiency labels don't provide enough information for buyers to make an informed choice."
Evaluating contrasting sets of F and B rated tyres (175/70 R14) on the road, the Emission Analytics' test route incorporated a range of steady-state speeds from 40mph to 70mph on normal road surfaces in consistent ambient temperatures. The tests employed the same test vehicle with the same driver.
Overall, the B rated tyre delivered superior performance in the 40-70 mph range, by an average of 3.8% mpg and 3.4% less CO2. There proved little difference at mid-range speeds, but a performance gap was clear at 55mph, and by 70mph fuel economy has improved by a substantial 12.9%.
From a buyer's perspective, this means that opting for B-rated tyres is unlikely to produce a fuel saving if journeys are mainly confined to urban routes. In contrast, opting for the same tyres and covering a substantial amount of motorway miles could produce a noticeable improvement.
Introduced in November 2012, the EU's mandated tyre label includes a test-bench-measured, rolling-resistance coefficient expressed as a fuel efficiency rating. However, with no linear relationship between rolling resistance and real-world fuel economy, better testing and modelling would allow buyers to make informed choices and select the tyres that will deliver a tangible fuel saving.
Market research shows that the current mandatory tyre labelling system is not proving effective.
A report compiled by the National Tyre Distributors Association (NTDA) and Lanxess, the manufacturer of high-tech rubber for tyres, found that one year after their introduction 93% of tyre retailers stated customers never or only occasionally requested information on the label.
In addition only 30% knew that tyre choice could affect fuel consumption. (Source: Fleet News)