The NTDA reports that it remains “firmly committed to its 3mm Tread Safety campaign, an initiative designed to raise awareness among motorists of the importance of changing tyres when they reach a 3mm tread depth rather than the lower, legal limit of 1.6mm, which was launched in partnership with Roadsafe in 2005.” The NTDA statement follows comments made by well-known manufacturer Michelin at the end of September in opposition to 3mm tread depth tyre change philosophies.
The 2005 NTDA 3mm campaign followed 2003 research by the British Rubber Manufacturers Association (BRMA) which commissioned MIRA to study the effects of tread depth on stopping distances. The study was carried out on MIRA’s test track in Nuneaton, and 5 different tread depths were tested – 6.7mm, 4.1mm, 2.6mm, 1.6mm (the legal minimum) and 0.9mm.
This research showed that the stopping distances in the wet start to increase dramatically at tread depths of below 3mm. It also showed that at the legal minimum tread depth of 1.6mm, the stopping distance increased by 36.8 per cent on hot rolled asphalt and 44.6 per cent on smooth concrete.
NTDA chief executive Stefan Hay commented: “Naturally, the NTDA does not want to become embroiled in a difference of opinion between manufacturers or comment on specific products and we are certainly not going to be distracted by a debate on wastefulness, individual product performance or fuel consumption. We are looking at this purely from a safety perspective and decades of both independent and manufacturer’s research shows that generally performance, particularly wet grip, gets worse as the tread wears. This is more marked as the tyre wears below 3mm of tread and approaches the legal limit. Let’s be clear, this is not about selling tyres, this is about the safety of UK motorists”.
The NTDA’s statement concluded by adding: “Many subsequent research projects have confirmed the results and safety organisation RoSPA, for example, still recommends that tyres are changed once the tread reaches 3mm in depth. The RAC still states that motorists need to be aware that even though the legal minimum tread depth is 1.6mm, in the rain anything less than 3mm can affect performance and the AA says check tread depth more often once it gets down to 3mm and aim to replace tyres before the tread wears below 2mm.”