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).
Arguments from tyre makers regarding standard versus over-size tyres and discrepancies in actual tyre dimensions.
| Identifier | ExFiles\Box 81\1\ scan0140 | |
| Date | 15th July 1914 | |
| R.{Sir Henry Royce} 235A (150 H) (W. W. 604. 15-7-14) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 0702. WoR{Arthur Wormald - General Works Manager}/Mcr2/B31714. -2- upon these as a possible new standard." The arguments used by the tyre makers were that the standard size was the one adopted because it was correct and that an over-size tyre was weak and mechanically unsound, and that one could not get the same strength in the over-size as you have in the full size designed for the larger rim. The bead of the over-size only corresponds with the bead of the standard tyre, and therefore is not of the same strength as the normal size. I recently went to some trouble in measuring up a number of makes of tyres obtaining the exact diameter and comparing this with the nominal diameter. If we take 895 x 135 tyres the nominal diameter is 35.2". With the exception of Palmer tyres, all the other well known makes are considerably smaller than this. Dunlops, for instance, being more than 2" short in diameter or 9" short in circumference. Thus it seems pretty evident that tyre manufacturers, during the period of high prices, have been in the habit of cutting down the actual size of their tyres, although selling them at the same | ||