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).
Brooklands tests to determine the effect of different tyre types on maximum speed and power losses.
| Identifier | ExFiles\Box 97\5\ scan0344 | |
| Date | 4th May 1939 | |
| 400a + 1320 To By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to Da{Bernard Day - Chassis Design}/Ev.{Ivan Evernden - coachwork} Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden}4/JH.4.5.39. Brooklands tests to determine the effect on maximum speed of the varying power losses reputed to be obtained with differing types of tyre. Chassis used for test - 7.B.V. - having a 1.2 : 1 overdrive gear, 10 x 43 axle ratio, and being fitted throughout with 6.50 x 16 tyres. Air temperature during tests 11°C. [Table Data] Headers: Type of tyre. | 1 mile. m.p.h. | Max lap speed m.p.h. | [Engine r.p.m.]* | Tyre pressures lb/in.2. cold. Front. | cold. Rear. | hot. Front. | hot. Rear. Row 1 (Michelin Pilote): 90.4 | 88.0 | 3700 | 22 | 22 | 26 | 27. Row 2 (Avon): 89.3 | 88.38 | 3660 | 26 | 30 | 33 | 38½ Row 3 (India): 86.6 | | 3580 | 25 | 28 | 32 | 35. Row 4 (Dunlop Track racing): 93 | 90.06 | 3850 | 45 | 45 | 47 | 47. *Table Note explaining column 4: Engine r.p.m. with respective tyres. | ||