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).
Report showing the effect of low tyre pressure on wheel revolutions per mile for speedometer readings.
| Identifier | ExFiles\Box 59\2\ Scan012 | |
| Date | 4th February 1930 | |
| X 4308. EFC. From Hs{Lord Ernest Hives - Chair}/AJL. Hs{Lord Ernest Hives - Chair}/AJL.1/MJ.4.2.30. SPEEDOMETERS. In reply to your EFC2/AD3.2.30., the following figures show the effect of low tyre pressures on the figure for road wheel revolutions per mile in the case of - (1) 33"x 6.75" Dunlop Silent Tread tyre on S.S. car 19-EX(rear). Tyre pressure lbs/sq.in. | 40 | 35 | 30 | 25 | 20 -----------------------------|-------|-------|-------|-------|------- Wheel Revs/mile. | 609.2 | 612.2 | 615.2 | 621.2 | 627.3 2.97 o/o increase (2) 19"x 6" Dunlop Silent Tread tyre on 20HP. car (14-G4). Tyre pressure lbs/sq.in. | 40 | 35 | 30 | 25 | 20 -----------------------------|-------|-------|-------|-------|------- Wheel Revs/mile. | 662.5 | 666.1 | 670.5 | 675.9 | 683.1 3.11 o/o increase Hs{Lord Ernest Hives - Chair}/AJL. | ||