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).
Table of engine RPM versus MPH for different gears, based on an actual tyre diameter under load.
| Identifier | ExFiles\Box 75\1\ scan0298 | |
| Date | 5th June 1924 | |
| +4247 5.6.24. ACTUAL TYRE DIA. UNDER LOAD 31.4". This gives :- M.P.H. Engine R.P.M. Direct 10 487 60 2922 2nd. 10 791 40 3164 1st. 10 1542 20 3084 Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||