In practice, constructors build their racing cars much lighter than the regulations require, and then bring them up to the mandatory minimum by adding ballast as low down as possible, and where it will best improve the vehicle's handling and reduce its tyre wear.
In a statement on Monday, Charles Hurst said the vehicle had not been supplied for anyone individual and that the tyre contract was awarded by the government's central procurement agency rather than directly by the Fire Service.
The US government will drop an investigation into the Ford Explorer requested by tyre maker Firestone over a series of fatal accidents involving the vehicle.