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).
Lap speeds with different tyre configurations and petrol consumption comparisons.
| Identifier | ExFiles\Box 160\4\ scan0039 | |
| Date | 13th March 1939 | |
| -2- Rm {William Robotham - Chief Engineer} /TAS. {T. Allan Swinden} 9/JH.13.3.39. An air speed indicator uncallibrated and fitted inside and outside the scoop, for purposes of comparison only, gave a reading of approximately 80 m.p.h. in each position. It should be noted that horns, body cross members, and fog lamp all combine to cause swirl and prevent air which enters the bottom portion of the radiator grille from playing effectively on the sump. Tyres. All tests had to be run with 18 x 5.50 road racing tyres on the front. 19 x 6.50 road racing tyres were tried on the front but had to be abandoned due to fouling after two practice laps at speeds over 90 m.p.h. The following lap speeds were obtained :- Front tyres. Rear tyres. Lap. Dunlop Road racing Dunlop road racing m.p.h. 18 x 5.50 19 x 6.50 105.97 Dunlop Road racing Dunlop track. 107.10 18 x 5.50 19 x 6.50 Hence the change from a studded tyre to a smooth tyre on the back wheels gives an increase in speed of 1 m.p.h. It is reasonable to assume that this increase would be at least doubled by the use of smooth tyres and 19" wheels on the front, especially as this would have the effect of lifting the car further from the ground. Petrol Consumption. The following are figures obtained with the Century Buick and the Paulin. The two cars ran together on the trips to and from Brooklands. Derby to Brooklands. Buick - Av. 45 m.p.h. - 11.4 m.p.g. Paulin - - 17.5 m.p.g. Brooklands to Derby. Buick - Av. 40 m.p.n. - 12.9 m.p.g. Rm {William Robotham - Chief Engineer} /GR. {George Ratcliffe} Paulin - - 24 m.p.g. Rm {William Robotham - Chief Engineer} /TAS. {T. Allan Swinden} | ||