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 calibration variations due to temperature and tyre pressure.
| Identifier | ExFiles\Box 82\1\ scan0186 | |
| Date | 9th August 1933 | |
| -2- Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}2/KT.9.8.33. designers insisting that there should be some spring controlled movement. Speedometer. We are sending you a calibration of a typical A.T. speedometer showing the variation with temperature. We are naturally alarmed that your speedometer reads low as Wst. assures us that it should be correct at any temperature you are likely to attain. It is possible that the hot weather has made your tyre pressures rise and therefore increased your effective rolling circumference. Will you please check the temperature of the speedometer and the tyre pressures under the conditions where you get a speedometer reading 3 m.p.h. slow at 80. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} | ||