From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Tyre selection, performance, and failures during the Nairobi Run for car 34-EX.
| Identifier | ExFiles\Box 114\4\ scan0076 | |
| Date | 5th March 1937 | |
| 1011 35 Sg.{Arthur F. Sidgreaves - MD} from Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} Hs.{Lord Ernest Hives - Chair} C. Cx.{Major Len W. Cox - Advertising Manager} Bkl. Rm{William Robotham - Chief Engineer}/Gry{Shadwell Grylls}/R.5.3.37. 34-EX - NAIROBI RUN. SE/E.4.3.37. The two possible types of tyre for this car were 7.50 x 18 and a lorry tyre "Giant". The former was chosen because at the minimum pressure recommended by Dunlops for sand it had the bigger area of contact. It also meant less alteration to the car. The car was equipped with two spares and carried in addition 10 tubes all treated with liquid to seal small punctures from "Desert Thorn". In Dunlop's opinion the car should have been able to go to Nairobi and back on one set of tyres. They quote as an example a Riley car (of course lighter than 34-EX) which after 6,000 miles' running went to the Cape and back on the same set of tyres. We are now very sorry that we did not arrange a supply of tyres at all aerodromes en route, but Dunlop's say that the mileage we get from tyres in France bears no relation to the African conditions. They have wired Symons their recommendations for the two kinds of tyre burst; less pressure for a "concussion" burst and more for failure of the side wall. They say it is also possible that the treads have worn away through excessive wheel spin in the sand. Until we, or Dunlops, see the tyres we shall not know the real cause of the trouble. Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} | ||