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 excessive front tyre wear on the Wraith model, comparing it to the 25/30 HP.
| Identifier | ExFiles\Box 109\5\ scan0184 | |
| Date | 11th November 1939 | |
| c to Rm.{William Robotham - Chief Engineer} 661 BY/SB.{Mr Bull/Mr Bannister}10/HR.11.11.39. re WRAITH TYRE WEAR. ----------- It is understood that complaints of excessive or uneven front tyre wear, on Wraith cars, are being received. Investigation prior to the outbreak of war showed that front tyre wear on the Wraith was more pronounced than on the solid axle type of 25/30 HP., for the following reasons:- (a) Assuming the geometry of the suspension to be reasonably correct, our experience coincides with that of other manufacturers, namely, that independent suspension as such, does not cause increased tyre wear, but very definitely encourages faster driving both on going into a corner and when traversing rough surfaces, and this inevitably increases the rate of tyre wear without the Owner appreciating that the tyres are suffering as a result of his driving. If a Wraith were driven continuously at the same speed as a solid axle 25/30 HP., the tyres would probably last as long, but this is rarely the case, and we must therefore expect front tyre wear to be more rapid than formerly. (b) Reasons which existed on the old 25/30 HP. for a toe-in of something like 3/16" no longer exist on the Wraith. The toe-in was merely a relic of the days when we had heavily cambered front wheels, i.e., wheels leaning outwards, but as this geometry no longer exists today, we can see no need for much toe-in. It is recommended, therefore, that the toe-in be reduced to negligible proportions, say 0 to 1/16" toe-in. BY/SB{Mr Bull/Mr Bannister} | ||