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).
Different tyre sizes and their impact on wheel wobble tests.
| Identifier | ExFiles\Box 42\1\ Scan040 | |
| Date | 2nd February 1926 | |
| To BJ. from Hs.{Lord Ernest Hives - Chair} c. to EY. c. to Wor.{Arthur Wormald - General Works Manager} V3809 Hs{Lord Ernest Hives - Chair}1/LGE2. 2. 26. V3809 V235 WELL BASE WHEELS AND TYRES. With reference to BJ3/E17.2.26. We believe a certain amount of the confusion has arisen because we are using three sizes of tyres in our wobble tests. (1) 6" section tyre fitted to 21" well base rims. These are the tyres which are fitted to R's car at Le CanadelHenry Royce's French residence. When run with the same pressures as we use on the present straight sided tyre they are worse for steering wobbles. This we attribute to the increase in section and the better non-skid tread. (2) 6.75" semi-balloon tyres fitted to 21" well base rims. These larger section tyres can be fitted to the same rims and wheels as the 6" tyres. Normally they are intended to run at lower pressures - 30 to 35 lbs. These tyres are definitely worse than the present standard straight sided tyres for wheel wobble. (3) 7.3" section balloon tyres fitted to 20" well base rims. These are the original full balloon tyres. Their normal pressure is 18 to 25 lbs. They are easily the worst tyres for wobbles because of minimum internal damping and low inflation pressure. This type of tyre is not recommended. They are merely used as a means of measuring what margin of safety any particular anti-wobbling device is likely to have. Throughout our reports we have always contd:- | ||