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 Dunlop detailing the results of rolling resistance tests on two different tyre types.
Identifier | ExFiles\Box 53\2\ Scan254 | |
Date | 1st October 1926 | |
X4565 DUNLOP RUBBER CO.,LTD. TELEGRAPHIC ADDRESS: "DUNLOPS, BIRMINGHAM" TELEPHONE: BIRMINGHAM CENTRAL 4108 P.B.E. 25 LINES YOUR REF: Hs{Lord Ernest Hives - Chair}/Rml/LG. Expl.Dept. OUR REF: AH/CDL/C. FORT DUNLOP ERDINGTON BIRMINGHAM 1 October 1926. Messrs. Rolls Royce.Ltd. Nightingale Road, DERBY. Dear Sirs, Rolling Resistance of 33/5 and 33/6.75 Tyres. Further to our letter of the 27th.ult., we are now able to give you a little more information on the above subject. We have tested a 33 x 5 High Pressure Tyre and a 33 x 6.75 Balloon Tyre on a machine similar to the one used for our previous tests for you and reported in our letter of the 10th.November 1925. The results of these tests are shown in Fig.1 (attached). The rolling resistance of the 33 x 5 tyre at 45 lbs/sq.in. is 23 lbs.per ton, and of the 33 x 6.75 balloon tyre at 30 lbs/sq.in. - 38 lbs. per ton. These tests were made at a speed of 50 m.p.h., and the actual load on the tyre in each case was 1320 lbs. A second test was carried out under actual road conditions in order to determine the effect on a car's performance of these two types of tyres. A car weighing 2 tons 11 cwt. (back axle 28 cwts, front axle 23 cwts) and fitted with 33 x 5 tyres was allowed to run freely from rest down a hill, (straight road, tarmac surface) and at the bottom of the hill was allowed to continue rolling along the level until it came to rest of its own accord. The total distance rolled was measured, this being done at three different inflation pressures. The 33 x 5 tyres were then replaced by 33 x 6.75 balloon tyres and the test repeated, the results being shown in Fig.2. Continued.... | ||