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).
Comparison table of various Dunlop wheels and tyres for a 20 HP vehicle.
| Identifier | ExFiles\Box 106\4\ scan0100 | |
| Date | 14th November 1928 guessed | |
| 20 HP. WHEEL AND TYRE COMPARISONS (DUNLOP WHEELS & TYRES). | Type of tyre and wheel. | Effect: running circum: ins. | Effect: running dia. ins. | Circum: with no load.ins. | Dia. with no load. ins. | Weight lbs. | Remarks. | |------------------------------|------------------------------|---------------------------|---------------------------|-------------------------|-------------|---------------------------------------------------------------------------------| | 32 X 6" on 20" rim. | 97.25 | 30.8 | 100.5 | 31.9 | 59.5 | This wheel and tyre has been recently standardised. | | 32 X 6" (Z) on 20" rim. | 99.125 | 31.55 | 103 | 32.8 | 65 | Marked as the above plus Z. A heavy duty reinforced tyre. Received instead of standardised tyre. | | 5¼ on 21" rim. | 97.5 | 31 | 100.75 | 32.1 | 59 | Previous standard. | | 5¼ on 21" rim. (Z). | 98.5 | 31.45 | 101 | 32.15 | 60.5 | As above by heavy duty reinforced tyre. | | 33 X 6" on 21" rim. | 101.5 | 32.4 | 104.5 | 33.25 | 62.5 | Never standardised. | | 31 X 6" on 19" rim. Narrow hub. | 94.625 | 30.15 | 98.375 | 31.4 | 57 | As fitted to 12-G-4. | All the figures above taken under the same conditions of load and 35 lbs/sq.in. pressure. All new tyres. Comparison of tyre section. 32 X 6 and 32 X 6.Z. | Tyre. | A.{Mr Adams} | B. | |------------|---------|--------| | 32 X 6 | 4" | 5.8" | | 32 X 6 Z. | 4.25" | 6.0" | | ||