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).
Tyre performance, steering wobble, and the effect of tyre pressure on selectiveness.
| Identifier | ExFiles\Box 29\1\ Scan241 | |
| Date | 1st September 1926 guessed | |
| contd :- -2- noted that though we have some 6.75" tyres worn to the canvas and very uneven, they will not wobble even with no dampers. Another point of interest is that unless we add a lot of friction to the steering, balloon tyres are definitely preferable to high pressure tyres for control and shocks. We feel we ought to run more cars with this axle and 6.75" tyres in France with a view to adopting them as standard - they seem to have many advantages and few disadvantages now that light shunting steering has been obtained. Certainly they seem to be the best thing to use with well base wheels. With standard side steering tube, 2000 lbs. springs and 5 1/2 lbs. friction in the steering, we can still get a wobble to build up with no dampers and the worst 6" tyres. We are trying 1500 lbs. springs with less set-up, also the reversed leaf road springs. 6.2" Michelin and 6.75" Dunlops can be run down to 30 lbs/sq.in. on the rear without making the steering wander, below that they rapidly spoil the selectiveness. Nevertheless, for normal tyres and side steering tube springs, wandering is mainly a matter of the correct weight on the back and good damping. A strange fact is that if the rear tyre pressure is lowered too far, shocks on the contd :- [Graph text] Y-axis: SELECTIVENESS. X-axis: TYRE PRESSURE LBS/SQ. IN. | ||