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).
The performance tests of balloon tyres compared to normal cord tyres.
| Identifier | ExFiles\Box 53\2\ Scan057 | |
| Date | 13th September 1923 | |
| Hs.{Lord Ernest Hives - Chair} from Rn.{Mr Robinson} X.4565 Hs{Lord Ernest Hives - Chair}/Rml/LG13.9.23. BALLOON TYRE TESTS. These tyres were, first of all, inflated to 20 lbs. per sq.in. all round but as the riding qualities did not appear to be equal to the tyres we tried on the 40/50 HP., the pressure.was lowered to 15 lbs./sq.in. all round for the tests. The tractive resistance figures show that the rolling resistance of the balloon tyres is somewhat greater than that of the normal cord tyre - say 20%. The acceleration and speed tests show an apparently better power transmission efficiency for the normal cord tyre. This could be readily checked by taking power curves on the dynamometer consecutively with the two sets of tyres. In conclusion we should say that at an inflation pressure of 20/25 lbs.per sq.in., the losses due to fitting balloon tyres would make little difference to the petrol consumption as regards rolling, but require investigation for hysterisis losses. [Handwritten insertion] about 2% at 20m.p.h. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} [Handwritten text] The balloon tyres which shewd little difference in performance to the cord tyres on the 40/50 were inflated to 25lbs/sq" front & 30lbs/sq" rear. Perhaps our 15 lbs/sq" is too low for useful comparison? | ||