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).
Axle ratio experiment on a 25/30 HP car by fitting larger tyres to simulate the effects of different gears.
| Identifier | ExFiles\Box 108\1\ scan0347 | |
| Date | 14th February 1938 | |
| To. Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} 600a CHATEAUROUX 7/.I4.2.38. 26.G.VI.- 25/30 HP. Axle Ratio. Thank you for your memo Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}4/AP.I2.2.38, in which we note that you will not be sending out Phantom III axle gears for this car. As an experiment, we have fitted on the rear, a pair of 7.50 x 17" Fort Dunlop Covers which have been in the garage for some years. These give 7½-8% increase in effective circumference, so we shall be able to get a fair idea of the maximum loss of performance we should be likely to experience with P.III. gears, which I believe would give a 6.8% increase. The reduction in skidding on wet roads and increased steadiness of the rear of the car on corners was at once apparent. -------- Rm{William Robotham - Chief Engineer}/IMW.{Ivan M. Waller - Head of Chateauroux} Ivan M.{Mr Moon / Mr Moore} Waller. | ||