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 tyre pressure tests and the causes of steering wobble on chassis 9-G-111.
| Identifier | ExFiles\Box 29\1\ Scan014 | |
| Date | 24th August 1925 | |
| COPY. Hotel de France, Chateauroux, Indre, France. GWH{George W. Hancock - Head Chateauroux}1/Crn24.8.25. To Hs.{Lord Ernest Hives - Chair} From G.W.Hancock. ---------------- CHASSIS 9-G-111. ---------------- We have received your letter of the 22nd. inst. and have noted the comments therein. All our tests carried out with standard Dunlop tyres. The pressures were - front 40 lbs. per sq.in. rear, 45 lbs. sq.in. We had them, for one week only, 45 lbs. front and 55 lbs. rear, but we dropped them again because of the hot weather. Actually, these pressures, after the car has run a few miles, would be 45 lbs. front and 50 lbs. rear. We have always checked our tyre pressures carefully, and we do not run tyres after shewing canvas. This is for safety. We have not, at any time, run with high pressure tyres for any time, only in our experimental tests, which were given together with the reports. We have full records of all tyres used during the test of 93-NK over here. These, if you wish them, can be despatched immediately. Our explanation of the steering wobbles developing up on 93-NK was that we received tyres and tubes which were afterwards found to be very much out of balance - tubes long valve type, and our variation of results of tests was due to the quick wear of front tyres, which meant the continual changing of same, which before it was noticed we had one day tyres practically balanced, and another day they would be very much out of balance. We got to the bottom of this trouble, and drilled our wheels so that we could balance all tyres up, after which the wobbles were almost extinct - as our reports shew towards the end of the test. Our experimental tests prove to us that with higher tyre pressures the wobbles were almost negligible, but what we did complain of with higher pressures was that it made the steering more unstable, i.e., a pot-hole would cause the car to dive very easily across the road, the steering feeling very light. G.W.Hancock. | ||