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).
Graph showing tyre horsepower versus inflation pressure, submitted by Dunlop.
| Identifier | ExFiles\Box 160\2\ scan0019 | |
| Date | 1st June 1922 guessed | |
| X4578 CURVES SUBMITTED TO US BY MESSRS. DUNLOP. 1,120 lbs. per tyre. 32 X 4 1/2 cord tyre. 50 m.p.h. H.P. I.P. 3 2 1 40 60 80 | ||