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).
Tyre pressure experiments, their effect on comfort, and mileage.
| Identifier | ExFiles\Box 45\1\ Scan077 | |
| Date | 1st September 1920 | |
| Contd. -2- Hs{Lord Ernest Hives - Chair}2/LG1.9.20. tyres we reduced the pressure to 55 lbs., the car was entirely different. The increase in comfort and the riding to obtain by the lower tyre pressure in something which we have not been able to obtain by any other means. The American Goodyear tyres have printed on the covers "Inflate to 81 lbs." We do not agree with this because we consider that the pressure should be in some relation to the weight carried by the tyre. Our tyre mileages on experimental cars do not confirm that high tyre pressures give the longest mileage. We are now in the process of carrying out careful comparative tests with Dunlop straight-sided tyres, running running them at different tyre pressure. As this means running tyres to destruction, it will of necessity be a long job. We have, however, used up one set on the rear wheels which we ran at 70 lbs. pressure. These tyres only lasted 2700 to 3000 miles respectively. They did not burst but all the rubber was worn off the thread and the first layer of canvas. This is very bad mileage for rear tyres as our average tyre mileage is between 5000 to 6000 miles when run with 65 lbs. pressure. The Dunlop people, when they first supplied us with straight-sided tyres, wished us to run with high pressure but we pointed out to them that we did not like tyres which demanded high tyre pressures. They afterwards agreed that front tyres on Rolls-Royce cars need never be pumped harder than 65 lbs. pressure‡ The pressure of the rear tyres will be decided by experimenting as stated previously. Contd. | ||