Letter from Dunlop Rubber Co. Ltd. detailing experiments on effective tyre diameter at high speeds.
| Identifier | ExFiles\Box 157\3\ scan0143 | |
| Date | 25th June 1925 | |
| COPY From: DUNLOP RUBBER CO., LTD. Fort Dunlop, Erdington, Birmingham. C.A.R 1332 Research Department. 25 June 1925. Messrs. Rolls Royce Limited, Nightingale Road, DERBY. Dear Sirs, Effective Tyre Diameter at High Speeds. Further to our letter of the 20th., we have now made some experiments to determine the effective radius of our 33 x 5 tyre at various speeds. Unfortunately we have no facilities at the moment for testing at speeds higher than 50 miles per hour, except on the racing track, where the conditions render it almost impossible to obtain data. In the near future we hope to have completed a new machine capable of much higher speeds than those you mention. The curve attached shows the increase in radius in millimetres at all speeds up to 50 miles per hour, and by extrapolation it is estimated that in the range 70 to 90 miles per hour the increase is roughly proportional to the square of the speed. The curve was obtained with the tyre at 70 lbs. pressure. At 50 lbs. the increase was 40% greater, i.e. 8 to 11 mms. The load on the tyre was 1320 lbs. We shall be glad to give you any further data we may obtain in the future. Yours faithfully, Sgd. A.Healey. for DUNLOP RUBBER CO.LTD. | ||
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).