Tyre wear, road testing experiences, and an investigation into poor fuel economy on a 'Silver Ghost' with 4-wheel brakes.
| Identifier | ExFiles\Box 160\5\ scan0361 | |
| Date | 28th October 1941 guessed | |
| - 6 - It was always very difficult to find the rim, although one could usually keep an eye on the tyre as it bowled down the road ahead of the car. In really hot weather, when driving fast on bad roads, which were the rule rather than the exception, tyre-life was very unsatisfactory. I remember leaving a town about 100 miles south of Orleans, at ten o'clock in the morning, to run someone to Dieppe, and then go on to Paris. I started with a brand-new set of 5 tyres, and ran into Paris about 11 o'clock at night, with one cover stuffed with hay. It is difficult to overestimate the value of having straight, traffic-free roads available for experimental testing and when, in addition, one is no longer worried by the Production Departments at the Factory, it is surprising what useful work can be accomplished. We had one rather puzzling problem when we first introduced 4-wheel brakes on the 'Silver Ghost1907 40/50 historic RAC 15,000 miles trial'. We found that the average petrol consumption over roads which we knew well, had dropped by over a mile to the gallon which - since at the time were were getting only about 11 miles to the gallon- was something which could not be disregarded. The modifications which we had made to the engine in fitting these brakes were insignificant and confined to a new exhaust manifold. The gear ratio and the weight of the car remained unaltered. The poor fuel economy, therefore, appeared to be inexplicable. As a last resort, I instructed the drivers to carry out a test-run using nothing but the handbrake which operated only on the rear wheels. Our mile to the gallon was at once recovered, showing that good brakes increase the average speed of the car and so the fuel consumption. | ||
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).