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).
Blueprint graph showing performance data for different back axle ratios and tyre sizes.
| Identifier | Morton\M22\ img078 | |
| Date | 5th May 1921 guessed | |
| BACK AXLE 16 x 52 BACK AXLE 15 x 52 BACK AXLE 14 x 52 ( TYRES) MILES PER HOUR 35 40 45 50 55 60 65 70 75 | ||