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).
Feasibility and implications of fitting 7½ inch tyres on Phantom III cars.
| Identifier | ExFiles\Box 158\1\ scan0153 | |
| Date | 18th November 1937 | |
| 7½" TYRES. 1339 S/W. Rm.{William Robotham - Chief Engineer} 7½" Tyres on Phantom III's. We think it would be very helpful if one or more P.III cars could be run on 7½" tyres on present standard wheels, in the same way that we are running larger tyres on Bentley present standard wheels, provided you are able to tell us that the clearance question concerning wheel arches, wings, etc. is no worse than it is on the Bentley. For instance, you have a P.III car running in Derby for various purposes on which you possibly could have 7½" wheels and tyres fitted in order to get some information about their life, their suitability for the car, their added comfort, etc. We were proposing also to try and run a car in London in such a way, and had in mind 3CM1 which is being fitted with an experimental body. This car, as you know, is already fitted with these larger tyres such as Mr.Symons used on his Nairobi run, but the car is weeks from completion yet and even then we do not know what will happen to it. In the meantime it might be possible for me to run some of these big tyres on my car 3-BU-190 if we know you take the view that they could be run on present standard clearances, wings, etc. without serious interference, or without seriously affecting the performance of the car because of the increased gear ratio. I believe you once told me that the increase in gear ratio was so slight as to be practically unnoticeable. Perhaps you would kindly confirm that this is so. Would you please let me have your views on this question generally. Cx.{Major Len W. Cox - Advertising Manager} -dub | ||