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).
Use and safety of security bolts for tires, referencing a customer incident and Dunlop's advice.
| Identifier | ExFiles\Box 53\1\ Scan124 | |
| Date | 26th September 1922 | |
| E.P. Have you any remarks please. The Dunlop case seems so feeble that I can hardly understand it. H 3/10/22 SECURITY BOLTS FOR TIRES. With reference to EP {G. Eric Platford - Chief Quality Engineer} 's Memo No. 257 upon the above subject, in which it is recommended that security bolts should not be fitted with Cord tires. I called to-day (22.9.22) upon Mr. H.H. Stuttard, owner of 4-CW. He told me that a Michelin Cable tire 895 x 150 came off the rim of the rear wheel of his car while travelling at about 50 m.p.h. This tire was not fitted with security bolts and was inflated to 55 lbs. pressure. He expressed his intention of always fitting security bolts in future. I warned him of the Dunlop Company's advice on this matter, but he replied that he would rather risk the possibility of punctured tubes than suffer a repetition of his recent experience. To my mind the letter from the Dunlop Company, quoted in the above-mention memo, is excessively weak. They say that the use of security bolts causes abrasions upon the tube which "reduces the inflation pressure, and by permitting the bead to move, allows the tube to get underneath it and force the bead over the rim". According to this theory, the pressure which is reduced sufficiently to allow the bead to lift is stil sufficient to force the bead up over the rim. This is evidently based entirely upon their own theory and is not borne out by their tests. As a matter of fact, their tests would appear to have been quite useless, for, apparently, they did not succeed in getting a tire to blow off a rim at all. To be on any value, tests would have to prove that tires will blow off the rims under certain conditions when fitted with security bolts, but will not do so under similar conditions when not fitted with security bolts - or vice versa. Deflation may occur from a number of causes, but, having occurred, it is hard to believe that the tire is as liable to come off the rim when fitted with security bolts as it is when not so fitted. Messrs. Dunlop's theory as to how the bead is lifted over the rims is possibly correct; but it must apply as much in the case of the tire not fitted with security bolts as it does in that of a tire which is so fitted - if not more so. | ||