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).
Investigation into incorrect tyre pressures caused by a faulty gauge and the resulting effects on tyre performance.
| Identifier | ExFiles\Box 45\2\ Scan152 | |
| Date | 23th April 1929 guessed | |
| (2) driver to use lower pressures than this, i.e., not exceeding 30 lbs. all round. The driver states that he ascertains generally about once a week what pressure is in the tyres and restores it to 30 lbs. Taking the driver's pressure gauge and testing the pressure in the tyres when the car stood at Fort Dunlop, it was found that in two of the tyres the pressure was only 15 lbs/sq.in., and in the other two, it was only 20 lbs. Thus, in two cases they were less than half, and in the other two, half the pressure asked for by the Rolls-Royce Co. This seemed to be so grossly wrong that we took the precaution of testing the driver's gauge, and found that, unfortunately, its reading was so erratic, having an error in some parts of 10 lbs/sq.in., that it had been evidently deceiving the driver for a long time. Testing with a correct gauge, it was found that two of the tyres were actually at 22 lbs. and the other two at 27 lbs. Arrangements were made, therefore, to provide the driver with the correct gauge, and it is concluded that probably from the very start nobody has known the real pressure in the tyres, and consequently Mr. Antweiler may have found quite a wrong impression in regard to the pressures he actually is running at. In any event, it is clear that the pressures found in the tyres are unnecessarily low, and this will bring about certain disabilities in connection with the tyres - for example, the extra deflection of the tyres due to the low pressure tends to close the grooves in the tyre at the point of contact with the road. The tyre surface, therefore, approaches that of a plain tyre and consequently it is not giving the circumferential ridges a chance to function at maximum efficiency. This would increase the tendency to pick up stones, to skidding and to wheel spin. With regard to the noise on granite sets, it must be recognised that no form of tyre, not even a plain tyre, would be free from this. The pattering of the tyre over the separate sets is bound to set up a noise which would be accentuated when the sets are wet. We, therefore, have a condition in which the tyres have been used at some unknown pressure, obviously very low, which prevents them from functioning properly, and it will be appreciated that on this account, and in view of the experience of the Rolls-Royce and other users, it would be probably premature to take for granted that the tyres are necessarily unsatisfactory. | ||