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).
Letter discussing the performance and comparison of different experimental balloon tires.
| Identifier | ExFiles\Box 53\2\ Scan092 | |
| Date | 11th January 1924 | |
| Oy11-E-21124 January 11, 1924. Mr. Claude Johnson, Rolls-Royce, Ltd., London, England. (Copy for attention of Mr. Royce " " " " Mr. Hives) Dear Sir: Re: Balloon Tires - Experimental Rpt./4565 We wish to thank Mr. Hives for his copy of report re balloon tires. The American Dunlop Company are proposing to develop in this country balloon tires on the wide-dropped rim used by Dunlops in England, and it is therefore most interesting to us to learn of the disadvantages of this type and compare them with our own types. We have run a Rolls-Royce test car 12,000 miles on Goodyear 32x6, four ply tires mounted on what is known as the "30x5" rim, 20" dia. On my own Hupmobile car I have run over 8000 miles on a set of Goodyear 30x5, 4 ply tires mounted on "29x4" rims, 20" diameter. These rims represent approximately the degree of "oversizing" which is now recommended by the American Tire and Rim Association. Both sets have been very satisfactory but with both sets it was necessary to tighten up rear shock absorbers to prevent "throwing" of the rear of the car on waves in the road, which in the Hupmobile was associated with a constant tendency to "pitch" or "gallop" at speed. The 34x7 tires have not been run any great distance but enough to show that the throwing tendency is more pronounced than with the 32x6. It may be well to add that the 32x6 corresponds closely (according to Mr. Macbeth of Dunlops) with the English 34x7 and the 30x5 with the English 32x6, i.e., that these American tires if mounted on the wide Dunlop rims would have similar dimensions to the English tire of next larger size. | ||