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).
Tests conducted on balloon tyres and their effect on high-speed wobbles and vehicle performance.
| Identifier | ExFiles\Box 29\1\ Scan282 | |
| Date | 4th March 1927 | |
| X457 To Sg.{Arthur F. Sidgreaves - MD} from Hs{Lord Ernest Hives - Chair}/An. c. to BY.{R.W. Bailey - Chief Engineer} c. to Bs.{A J. Barnes - Assistant Manager} BALLOON TYRES. X4565 We have conducted tests with balloon tyres on straight sided rims. These tyres were approximately 35 X 6.75". We actually compared these tyres with the present standard 6.75" balloon tyres on well base rims with reference to their susceptibility to high speed wobbles. We do not consider that these tyres are any worse than standard in this respect. As a result of other tests, we conclude that it is because this type of tyre has a large rotational moment of inertia which has proved to be a good palliative for high speed wobbles. We therefore see no objection to customers being supplied with 33 X 6.60" balloon tyres, provided that they adhere to our present instructions with regard to the front tyre pressure being kept at 40 lbs/sq.in. and at the same time the front of the car is equipped with hydraulic shock dampers. The gear ratio of the car will definitely be raised slightly by the larger dia. tyres, but customers who wish to go to the expense of larger tyres will be more concerned with comfort than performance or the slight loss of steering lock. Examination should be made to ascertain that the steering stops are correctly set when these tyres are changed. Hs{Lord Ernest Hives - Chair}/An. | ||