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).
Steering wobble issues in the 12-EX car, tracing the cause to Dunlop balloon tyres.
| Identifier | ExFiles\Box 17\3\ Scan034 | |
| Date | 18th August 1926 | |
| To Wor.{Arthur Wormald - General Works Manager} from Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} Hs{Lord Ernest Hives - Chair}/Rn{Mr Robinson}1/LG18. 8. 26. 47430 12-EX CAR. X235 X7940 Replying to BJ12/D16. 8. 26 attached. We have carried out a number of tests on the steering of 12-EX car in France. We find that the chief cause of the complaint which has been made about the steering is a set of 6" well base Dunlop balloon tyres. These are some of the first tyres of this type manufactured by Messrs. Dunlop; they were sent out to France with 8-EX car. For some reason these tyres have shewn themselves to be bad for high speed wobbles when they are new, and in addition have worn very unevenly which has made them still worse. With regard to the 2nd. para, of BJ's note - this is a low speed wobble and is chiefly due to the exceptional freedom of the steering on the new axle. We were able to eliminate it by the incorporation of a little friction. We do not consider that this need cause any anxiety. Briefly, the present position is this. We believe that the new axle will give satisfactory results with high pressure tyres. While we obtain quite satisfactory results with the 6.75 Dunlop and 6.2" Michelin balloon tyres, the peculiar behaviour of the 6" set which we have in France requires further investigation before we can say that this axle will be satisfactory with well base rims and tyres. We consider that the shock dampers, which are of course exactly the same as those used on the 20 HP, are quite satisfactory. The conditions set up by these 6" tyres are quite exceptional and very much worse than anything we have previously encountered. Possibly we shall find it necessary to alter the setting of the dampers to cope with such extreme conditions. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} | ||