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).
Letter from the India Tyre & Rubber Company comparing different tyre tread designs.
| Identifier | ExFiles\Box 29\4\ Scan156 | |
| Date | 23th November 1933 | |
| Y.5562 TELEPHONES: PAISLEY 4141/5. INDIA TYRE & RUBBER COMPANY, LTD. TELEGRAMS: INDIAOWL, RENFREW. INCHINNAN SCOTLAND OUR REF. PW/FGE YOUR REF. 23rd November, 1933. W.A. Robotham Esq., Experimental Department, Messrs. Rolls-Royce Limited, DERBY. Dear Sir, During a discussion with reference to the Speed Special Tread Design.we showed prints of different tread designs to Lord Rothes and he thought that you might be interested in having these prints. The method of taking the prints was to mount the tyre on an axle above a scale, to ink the tread and to bring the tyre down on a piece of tracing paper and then apply the designated load. On the prints the total area is taken and is the com-bined area of the buttons and the groove space between the buttons. The area of rubber in contact with the road is the actual area of the buttons. The length of the skid line is the length of the line at the edge of the buttons. INDIA S.N.S. means Super Nonskid and S.S. means Speed special. You will note that the area of the grooves in the Speed Special is 6.90" and the area of rubber in contact with the road is 16.27", while in the Dunlop the area of rubber in contact with the road is 18.14" and the groove space is 4.56". This means that we have a higher loading per square inch on the tread and a more open tread with a far longer edge line in contact with the road. While the Goodyear tyre has almost as much open space, the area of the rubber in contact with the road is only 12.25" which means a higher loading, but the edge line is only 51 5/8". We are returning to you, marked for your attention, two of/ | ||