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).
Tests conducted to determine the effect of tyre pressures on the performance of the 40/50 model.
| Identifier | WestWitteringFiles\K\June1923\ Scan36 | |
| Date | 1st June 1923 | |
| EFFECT OF TYRE PRESSURES ON 40/50 PERFORMANCE. We carried out tests to determine the effect of tyre pressures on - (a) Speedometer readings. (b) Acceleration and maximum speed. (c) Tractive resistance. (d) Petrol consumption. The tyres used for a, b, and c were Canadian Dunlop Cord, well worn (average mileage 5,000). hard tyres referred to - 90 lbs. per sq.in. soft " " " - 30 " " " (a) We found soft tyres caused the speedometer to read 1.5 m.p.h. fast at 30 m.p.h. (b) The fall in maximum speed due to soft tyres is just about balanced by the speedometer reading faster. That is, it is about 3 m.p.h. with a maximum speed of 60 m.p.h. The loss in acceleration is small. Accelerating from 20 m.p.h. over half a mile, soft tyres only increase the time taken by 3/5 secs. (c) By taking deceleration tests, we found the tractive resistance to be increased by 14 lbs. per ton (see print). (d) Petrol consumption taken at 20 m.p.h. with Dunlop S.S. Cords inflated to 90 lbs. per sq.in. and 25 lbs. per sq.in. - Inflated. Consumption. 90 lbs. per sq.in. 20.248 m.p.g. 25 " " " 18.704 m.p.g. Decrease in m.p.g. due to soft tyres - 1.544 on 20.248 m.p.g. = 6.87%. Hs{Lord Ernest Hives - Chair}/Rs.{Sir Henry Royce's Secretary} | ||