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).
Specification sheet for S.S. Chassis gear ratios, including engine and dynamo RPMs at various speeds.
| Identifier | ExFiles\Box 15\5\ Scan070 | |
| Date | 4th February 1929 | |
| X7310 4.2.29. S.S. CHASSIS GEAR RATIOS, ETC. The back axle ratio is 11/41 i.e. 1 : 3.727 The gear box ratios are :- Reverse 1 : 3.086 1st. 1 : 3.511 2nd. 1 : 1.998 3rd. 1 : 1.360 4th. 1 : 1.000 The effective tyre circumference for both types of tyre used is 103.25" So that the miles per hour at 1000 R.P.M. of the engine are :- Reverse 8.50 1st. 7.48 2nd. 13.13 3rd. 19.30 4th. 26.23 The following table gives the top gear engine r.p.m. and dynamo r.p.m. for various speeds in miles per hour. M.P.H. Engine R.P.M. Dynamo R.P.M. 10 381 572 12 457.5 686 15 572 858 20 762 1144 25 954 1430 30 1143 1715 35 1333 2000 40 1524 2290 50 1906 2860 60 2290 3430 70 2670 4000 80 3050 4575 EFC. | ||