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).
Standardisation and issues with balloon tyres for the 20 HP chassis.
| Identifier | ExFiles\Box 53\3\ Scan106 | |
| Date | 5th July 1928 | |
| X4565 W/S. c. BR.{T. E. Bellringer - Repair Manager} c. Hs.{Lord Ernest Hives - Chair} BY2/G.5.7.28. 20 HP. CHASSIS - TYRES. With reference to the standardisation sheet for the 20 HP. balloon tyres having dimensions 33" x 6" suitable for 21" rims, we have cleared up all the difficulties which previously existed, and we can be in the near future in a position to supply these for customers requirements. The two points which gave us trouble were :- (a) A special spare wheel carrier was carried at the back with a slight modification to the petrol tank and luggage grid. (b) Lower ratio bevel gears were necessary to keep the speed of the car unaffected and therefore the power from engine to tread of tyre the same. A serious issue, however, still exists, R.{Sir Henry Royce} is struggling hard, and has been for months to bring the floor level of the car down. The new tyre will push this dimension up above our present standard by .500". This being the case it appears to me that R.{Sir Henry Royce} would definitely set his face against using the balloon tyre for this reason alone. Before we commit ourselves I think this view of the matter ought to be thoroughly considered and R's opinion obtained, as it seems to me wrong at this stage of affairs to be considering a proposal which will actually lift the floor level which R.{Sir Henry Royce} is struggling so hard to reduce. From Dunlops latest list it would appear that they have a further size of tyre of which we have so far heard very little, the tyre in question fitting on a 20" rim instead of the present standard of 21" the new tyre size being 32" x 6", this size of balloon tyre being intermediate between the large 33" x 6" at present under consideration and Mr. Royce's further proposal of 31" x 6" fitting a 19" rim, and further since the diameter of the tyre is the same as our present medium pressure tyre it would appear that this represents a scheme which is worthy of consideration for immediate adoption, as it has a balloon comfort with the heights and clearances of the medium pressure. BY.{R.W. Bailey - Chief Engineer} BM | ||