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).
Speedometer accuracy and its impact on performance perception during an 'Autocar' road test.
| Identifier | ExFiles\Box 160\3\ scan0215 | |
| Date | 14th February 1939 | |
| 1379 W/S. Cx.{Major Len W. Cox - Advertising Manager} from Rm.{William Robotham - Chief Engineer} c. Bly.{B. W. Bleaney - Bentley Sales} Rm{William Robotham - Chief Engineer}1/R.14.2.39. 'AUTOCAR' ROAD TEST. With reference to Cx{Major Len W. Cox - Advertising Manager}11/KW.10.2.39., we pointed out to Bly.{B. W. Bleaney - Bentley Sales} that the speedometer on this car was unusually accurate. We now find that, generally speaking, no speedometer leaves the Works that is more than 2 miles fast @ 100 m.p.h. Such accuracy will, of course, handicap us in comparison with our competitors, but the Test Dept. say if they work to the reading agreed upon, which allowed them to be 6% fast, they occasionally get one back with caustic comments. The figures which we actually obtained on the 15,000 miles Exp. Overdrive Bentley gave a lap speed of 88.5 m.p.h. This is about the same as the standard Bentley without the overdrive. Briefly, B-2-M.R. was up to standard. We deprecate the practice of judging a car's performance by an unchecked speedometer reading to which has been added a hypothetical allowance. Rm.{William Robotham - Chief Engineer} | ||