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).
Issues with tyres and comparing American and Dunlop rim and tyre standards.
| Identifier | ExFiles\Box 19\4\ Scan063 | |
| Date | 24th June 1930 guessed | |
| -3- (1) mounting difficulty, (2) breakdown of side wall or "rim cutting", (3) chafing of inner tube (which we encountered), (4) also, to the proposal to adopt rims which at first were much wider than Dunlop's practice. In the course of the last three years, however, the Am. proposed standards have gradually come down to a width only slightly wider than Dunlops and which Dunlops are willing to adopt as a new standard. The use of such a slightly wider rim is considered beneficial in resisting shimmying tendencies which might otherwise be increased by the smaller wheel. Note 1. The Dunlop "silent tread" now R.R. standard is virtually our ribbed tread. In tractive effect it is under the worst conditions only 14% worse than the earlier Dunlop "buttress tread", which we found impossibly noisy. In resistance to side skidding it is 25% better. Also, Dunlops claim to have overcome the earlier tendency of ribbed tread tires to crack down to the fabric. These percentage differences are very small compared with the great differences which occur due to even very slight variations in inflation pressure. Note 2. The American makers have accepted the principle of the soft flexible "toe" to the bead which Dunlops have used and advocated on their D.C. tires and which prevents cutting of the tube and whipping of the tire off the rim when rim deflated. Note 3. Later: Test of 404-HH on Brooklands track on June 20 (reported in full elsewhere) makes it certain that it would be unwise from the point of view of safe steering to make any change in tire and rim equipment from present English standards without thorough and extensive tests. 07. | ||