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).
The testing of 7.50 tyres for the Phantom III model, detailing issues with wobble and steering.
| Identifier | ExFiles\Box 158\1\ scan0186 | |
| Date | 8th June 1938 | |
| W/S. {Derby Works / Sales} To Cx. {Major Len W. Cox - Advertising Manager} from Rm {William Robotham - Chief Engineer} /Gry. {Shadwell Grylls} c. Sg. {Arthur F. Sidgreaves - MD} c. Hs. {Lord Ernest Hives - Chair} c. By. {R.W. Bailey - Chief Engineer} Rm {William Robotham - Chief Engineer} /Gry. {Shadwell Grylls} 8/MH. {M. Huckerby} 8.6.38. 1339 7.50 TYRES FOR P.III. We have now run a set of these tyres made from the latest "C" type mould for half their life. 35-EX. with the correct setting of ball pad friction in the steering connections cannot be made to wobble on 7" tyres but is easily made to wobble on 7 1/2" tyres. Low speed wobbles are a customers' complaint on P.III. The maintenance of sufficient friction in the steering to prevent them is still a problem. We do not think more friction and consequently heavier steering which would be necessitated by 7 1/2" tyres would be acceptable. We cannot, therefore, recommend 7 1/2" tyres. When run at a pressure to give the same comfort the handling of the car undoubtedly suffers. We think Cx. {Major Len W. Cox - Advertising Manager} will agree that better stopping on a wet road has already been achieved by the 2000 tooth tyre. Rm {William Robotham - Chief Engineer} /Gry. {Shadwell Grylls} | ||