Major Court Treatt had had experience of Crossley vehicles during World War I when they were issued both as staff cars and tenders (light trucks) to all squadrons of the Royal Flying Corps. He also used one during his survey work for the air route and was pleased by how they coped with rough ground.
For the expedition they used two modified 25/30 chassis. These were a development of the Royal Flying Corps tender and were sold by Crossley with a variety of car bodies or with some adaption as commercial vehicles. Fitted with a four cylinder 4,536 cc petrol engine they were rated as having a 30 cwt payload. The expedition vehicles were modified in having raised suspension and a special body painted silver grey fitted with mosquito screens and with a roof that could be detached and converted into a raft to assist in river crossings. These were tested in the lake in Belle Vue gardens in Manchester but never actually used as they were abandoned not long into the journey to save weight.