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).
Comparison table of specifications for the Phantom III, 25/30, and Bentley models.
| Identifier | ExFiles\Box 142\1\ scan0222 | |
| Date | 27th September 1938 guessed | |
| Phantom III. 25/30 Bentley. Treasury rating. 50.7 29.4 29.4 Bore & Stroke. 82.5 x 114.3 88.9 x 114.3 88.9 x 114.3 Capacity. 7340 4257 4257 Cooling System. PF PF PF Position of valves & operation. 0 0 0 No. of main bearings. 7 7 7 Tank capacity & position. 33R 18R 18R. Chassis Lubrication 1 Shot 1 Shot 1 Shot. Speeds & gear lever position. 4R 4R 4R Type of Gear change. Syn. Syn. Syn. Normal top gear ratio. 4.25 4.25 4.3. Type of wheel. Wire. Wire. Wire. Size of Tyre. 7.00 x 18 6.50 x 17 6.50 x 17 Suspension front Ind Ind ½E " rear ½E ½E ½E *Overall length 17-7 17-6 16-0 Wheelbase. 11-10 11-4 10-6 Track 5-2.6R 4 - 11.5R 4 - 8 Clearance 8¾ 8 6.1 Turning circle. 48 - 0 46 - 6 40 - 11 Jacking system. Perm Perm - Overdrive top ratio - - 3.64 Thermostat YES YES YES *Size of rim 18 x 5 17 x 4 17 x 4. *Overall width. 6 - 5 6 - 1 5 - 8 | ||