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).
The handling of Bentley cars, comparing oversteer and understeer, with results from skid pan tests.
| Identifier | ExFiles\Box 155\4\ scan0027 | |
| Date | 11th March 1937 | |
| 1322. Sg.{Arthur F. Sidgreaves - MD} from Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} Hs.{Lord Ernest Hives - Chair} E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} By.{R.W. Bailey - Chief Engineer} Rm{William Robotham - Chief Engineer}/Gry{Shadwell Grylls}5/R.11.3.37. HANDLING OF BENTLEY CARS & OTHER TESTS ON SKID PAN. The earliest 3½-litre Bentley cars weighing about 30½ cwts handled very much better than the 4¼ type at 33 cwts of to-day. The reason for this is that the later cars with more weight on the back axle 'oversteer' more than the early cars. 5.B.IV car recently tried by Sales is an example of extreme oversteer. The amount that a car oversteers can be measured at varying sideways accelerations in about ten minutes on the skid pan. We set ourselves the problem of making 5.B.IV understeer. A brief explanation of understeer is that the faster a certain corner is taken the more rudder is required, since the slip of the front tyres is more than that of the rear. Oversteer is exactly the opposite. The advantages of an understeering car are:- (1) The car tends to keep a straighter course and does not wander. It, therefore, needs less attention and constant steering correction from the driver. (2) The tail does not 'tuck under' when cornering hard. The only disadvantage is that slightly more effort may be required if the understeer is obtained by increasing the front tyre slip instead of decreasing the rear tyre slip. After about fifty tests on the skid pan we achieved understeer by having different tyres front and rear and suitably adjusting the pressures, low in front and high at the rear. | ||