Question to the Department for Transport:

To ask Her Majesty's Government when the Department for Transport and its agents undertook research into the longevity of the life of safe tyres on Heavy Goods Vehicles; how many tyres were (1) selected for, and (2) actually used, in that research; and what steps they took to ensure that their research used controls to allow for the possibility that any changes observed in tyre material over time could have been caused by changes in the mix of the compound used by the manufacturers and not by deterioration.

The Government commissioned fundamental research to understand whether the material properties of a vehicle tyre change with its chronological age to such an extent that the integrity of the tyre, and therefore its safety, is compromised. 44 used tyres were selected as potential test samples, ranging from 3 to 19 years in age and originating from in-service use within the UK vehicle fleet. However, 18 of these tyres exhibited evidence of physical damage, under-inflation, penetrations or repairs and were rejected from the study. The remaining 26 tyres were included, alongside five new tyres for comparator purposes.

To limit the variability from differences in rubber compound, steel cords and construction, all the tyres selected were from the same manufacturer, and the same size and designated usage i.e. for front axles. However, three different tyre models were used, as no single model spanned the complete age range of the tyres selected for the study.