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 performance data for different 5.50/18 tyres under varying loads.
| Identifier | ExFiles\Box 29\4\ Scan155 | |
| Date | 22th November 1933 | |
| COMPARISON 5.50/18 (28x5.50) TYRES INFLATION PRESSURE 35 LBS. TABLE HEADERS: LOAD | INFLATED O.D. | EFFECTIVE RADIUS | % DEFLECTION | AREA OF RUBBER IN ROAD CONTACT | AREA OF GROOVES | LENGTH OF SKID LINE TYRE TYPES (Under each header category): INDIA S.N.S. | INDIA S.S. | DUNLOP FORT | GOOD YEAR H.D. (Note: Area columns include SQ.IN. units) TABLE DATA: Row: 8 CWT. Inflated O.D.: 30.31 | 30.31 | 29.95 | 30.02 Effective Radius: 14.25 | 14.25 | 14.15 | 14.12 % Deflection: 14.70 | 14.70 | 13.80 | 14.80 Area of Rubber (SQ.IN.): 14.68 | 16.27 | 18.14 | 12.25 Area of Grooves (SQ.IN.): 7.86 | 6.90 | 4.56 | 5.85 Length of Skid Line: 56 2/3 | 64 1/2 | 48 | 51 5/8 Row: 9 CWT. Inflated O.D.: " | " | " | " Effective Radius: 14.15 | 14.17 | 14.08 | 14.05 % Deflection: 16.37 | 16.00 | 14.95 | 15.91 Row: 10 CWT. Inflated O.D.: " | " | " | " Effective Radius: 14.07 | 14.09 | 14.00 | 13.95 % Deflection: 17.75 | 17.30 | 16.30 | 17.61 Area of Rubber (SQ.IN.): 19.73 | 18.44 | 20.50 | 15.25 Area of Grooves (SQ.IN.): 8.42 | 7.60 | 5.50 | 7.30 Length of Skid Line: 72 2/3 | 75 | 56 1/2 | 69 | ||