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).
The 'Embiricos' car run at Brooklands, detailing tyre changes and performance.
| Identifier | ExFiles\Box 160\4\ scan0103 | |
| Date | 18th July 1939 | |
| 1379 By.{R.W. Bailey - Chief Engineer} from Rm.{William Robotham - Chief Engineer} c. Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} Rm{William Robotham - Chief Engineer}5/R.18.7.39. EMBIRICOS RUN ON BROOKLANDS. On the preliminary run on this car we tried out the 6.50 x 16 tyres. It was at once evident that the car was under-geared, the revs. reaching 4,250 on the favourable stretches. We changed to 6.50 x 19 and the lap speed improved, max. revs. obtained being 3,750. The hour was run on these tyres. After the hour we managed to get hold of some 6" x 19 medium distance tyres, and these improved the lap speed by 1 m.p.h. possibly they are worth slightly more than this, but the conditions had deteriorated by the time we tried them out. If we are ever to use the small tyres, we shall have to have a different axle ratio, or a different overdrive ratio in the box. Rm.{William Robotham - Chief Engineer} | ||