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).
Specification table comparing two types of Dunlop wheels and tyres.
| Identifier | ExFiles\Box 58\1\ Scan060 | |
| Date | 31th August 1928 guessed | |
| DUNLOP WHEELS AND TYRES. Type of tyre and wheel. Effective running circumference. ins. Effective running diameter. ins. Circumference 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 & 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. Tyre marked 'Z' received instead of standardised tyre. | ||