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 outlining road speed calculations for the 1936 Le Mans car at 4,500 revs with various axle and tyre combinations.
| Identifier | ExFiles\Box 90a\4\ Scan147 | |
| Date | 4th May 1936 | |
| Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}12/KW.4.5.36. LE MANS CAR - 1936. | Axle | Tyre | Road Speed at 4,500 revs. allowing for increase of tyre size due to centrifugal force. No wear allowance. | |---------|----------|------------------------------------------------------------------------------------------------------------------| | 11 x 41 | 6 x 19 | 113.5 | | | 6.5 x 19 | 117.5 | | 12 x 41 | 6 x 19 | 124.0 | | | 6 x 18 | 120.0 | With the large engine, estimated correct ratio is 120 M.P.H. at 4500 R.P.M. | ||