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).
Performance graph for a high compression engine with different back axle ratios.
| Identifier | Morton\M7\ img069 | |
| Date | 5th May 1921 guessed | |
| BACK AXLE 16x52. BACK AXLE 15x52. BACK AXLE 14x52. (7.00 TYRES). 1500 1750 2000 ENGINE. - HIGH COMPRESSION. | ||