 In 1926/27, while the conversion was in progress, two six-car trains of 1906 Stock and 1920 Stock were borrowed from the Piccadilly line, the trailers fitted with smaller wheels to allow them to run in the smaller Central London tunnels.Fitting the air-doors reduced the number of seats, from 48 to 40 in the trailers and 42 to 30 in the motor cars.In 1933, the CLR passed with the rest of the Underground Electric Railways Company of London to the newly formed London Passenger Transport Board (LPTB).