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 tyre specifications listing size, type, inflated diameter, inflated width, and effective radius.
| Identifier | ExFiles\Box 45\2\ Scan358 | |
| Date | 2nd October 1931 | |
| MESSRS. ROLLS ROYCE LIMITED. 2.10.31. Tyre Size & Type. Infl.diam. Infl.width. Effec.radius. 4.40-19 'Fort'. 28.69 4.55 13.63 5.25-21 " 32.42 5.50 15.31 6.00-19 " 31.75 6.24 14.94 6.00-20 " 32.85 6.18 15.44 7.00-20 " 34.39 6.91 16.00 7.00-21 " 35.39 6.91 16.50 7.00-21 Standard. 34.95 6.67 16.30 - - - - - - - - - | ||