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).
Correspondence about the difficulty of fitting tires and tubes due to valve hole positioning on Dunlop rims.
| Identifier | ExFiles\Box 42\5\ Scan071 | |
| Date | 27th May 1931 | |
| [Handwritten notes at top: 83895, W, H] [Stamp 1: RECEIVED JAN 15 1931] [Stamp 2: RECEIVED JUN 1 1931] Btn-6 May 27, 1931. Rolls Royce, Ltd., Derby, England. Attention of Mr. Bailey. [Handwritten: Cc-Hs.{Lord Ernest Hives - Chair}] Gentlemen: Re: Tires and Tubes We have met a little difficulty in fitting tires on the Dunlop drop center rims owing to the hole in the rim for the valve being set in the side of the well, and also being a little smaller than is standard in this country, and being .500" diameter against American standard .562". On the early cars we tried tubes with central valves without enlarging the hole and found that this resulted in the valves pulling out of the tubes and going flat overnight, since it was not possible to make sure that the valve was quite free. We are getting over this trouble by having made special tubes with offset valves and by opening up the holes in the rims to .562" diameter. In this connection we quote from a letter of the United States Rubber Company who produce our tires: "Supplementing our letter of May 23rd on the above subject, we are of the opinion that the 7.00-20 tubes with the 3461 valve off-set should work satisfactorily on your 20x4.00 drop center wheel with the valve hole on the side of the well. However, as mentioned in our previous letter, it is very essential that care be used to see that the off-set valve stem points toward the outside of the wheel to properly match the valve hole, otherwise the tube is very badly strained and buckled at the valve base with the result that the valve stem is very likely to pull out during service. On this account, we urge you to consider placing the valve hole in the center of the well in order to eliminate this possible condition, and also to make it possible to use the standard American tubes which have the valve stem centrally located." This leaves us in the position of fitting an entirely special tube and makes the emergency replacement of a damaged tube rather difficult. This is mitigated a little by the fact that at present in nearly all cases we fit two spares. | ||