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).
Cost-benefit analysis of fitting Twin Tyres versus standard and oversize competitor tyres for heavy-bodied cars.
| Identifier | ExFiles\Box 81\1\ scan0122 | |
| Date | 13th February 1914 | |
| KM1/18. - 2 - 13th February 1914. size a set of four Square Tread Michelin tyres costs £29.16.0. To fit this rim our competitors offer the 895 x 150 oversize tyres, of which a set of four flat treads costs £45.16.0, an additional £16. In the event of the tyres supplied with the chassis not being sufficient owing to the fact that it is to be fitted with an exceptionally heavy body, we should under ordinary circumstances recommend the fitting of the next larger standard size in both rims and tyres, but as we do not list a larger section than the 135, the solution in the case of Rolls Royce cars, is provided by our Twin Tyres and in practically the whole of your cars we have dealt with in this way, the equipment of 880 x 120 tyres has been ample. The cost of a set composed of the 6. 880 x 120 Square Tread tyres necessary for the equipment of Twin Wheels is only £39.15.0 as compared with £45.16.0 for a set of 4 895 x 150 flat tread oversize tyres, so that the cost of a set of twin wheels and rims, viz. £24.0.0. even supposing the whole of this to be additional, would be entirely wiped out by the time that four sets of tyres had been used, and thereafter the fitting of twins would result in the clear saving of £6. on each complete set of tyres purchased. This is assuming that the tyres wear out in the same time in each case, but in practice the difference is (over) | ||