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).
Effects of different tyre types and corresponding gear ratios for the 20 HP Chassis.
| Identifier | ExFiles\Box 53\3\ Scan070 | |
| Date | 14th July 1927 | |
| X4565 To Hs.{Lord Ernest Hives - Chair} from BJ. Copy to BY.{R.W. Bailey - Chief Engineer} Copy to ROY.{Sir Henry Royce} Copy to D/BP Copy to Sg.{Arthur F. Sidgreaves - MD} Copy to C. Balloon Tyres on 20 HP Chassis. BJ2/E14/7/27 -------------------------------- The position appears to be as follows:- 1. The tyres we fitted in the past were high pressure and we used a standard gear ratio. 2. When we fitted medium pressure tyres with the standard gear ratio, the effect was that we got better results in running and we obtained an equivalent of half a tooth reduction in gear ratio. 3. If we adopt 6 inch balloon tyres with the present standard gear ratio, as is now suggested, we shall drop back to the position we were in in (1) above, namely, we shall be worse off than we were in number (2). 4. We should far prefer to arrange that, when we adopt 6 inch balloon tyres as standard, we should at the same time adopt the lower gear which has recently been tested for 10,000 miles, as this would give us the equivalent of half a tooth reduction in gear ratio, namely, the same as Number (2) above, which is satisfactory. In the meantime, we could of course supply 6 inch balloon tyres in special cases or complaints as agreed in the standardisation sheet which has been signed. 5. In regard to the distant future, we may obtain a smaller wheel for the 6 inch balloon tyre as suggested by R.{Sir Henry Royce}, which, with the reduced axle gear ratio, would give us a still better result as it would be equivalent to approximately 1 1/4 tooth reduction in gear ratio. BJ. [STAMP: RECEIVED 14 JUL 1927 H] | ||