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).
Internal memorandum discussing tyre choices and proposing a switch to larger, lower-pressure tyres to improve ride comfort and compete with other manufacturers.
| Identifier | ExFiles\Box 42\1\ Scan050 | |
| Date | 24th March 1926 | |
| Hs.{Lord Ernest Hives - Chair} To DA.{Bernard Day - Chassis Design} } FROM R.{Sir Henry Royce} LE CANADELHenry Royce's French residence. BY.{R.W. Bailey - Chief Engineer} c. to CJ. BJ. c. to E.{Mr Elliott - Chief Engineer} RG.{Mr Rowledge} X3809 R1/M24.3.26. PHANTOM & INDIA TYRES - re. X.4565 X.8820 Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}/15.3.26. X.3809 X.5820 X.8410 I have said previously that we shall be left behind unless we can give customers something better than ordinary high pressure tyres. Here the roads are so bad that cars would get broken up unless larger tyres and lower pressures were used. This applies to passengers, chassis, and body. The only fear I have against larger low pressure tyres is skidding and punctures; if they are reasonably good for these I feel sure their other faults are more than compensated for, even if one had to reduce maximum speeds to avoid high speed wobbles. The passengers for comfort, and car body for silence and life, demand less vibration, and I am sure that not only is this the easiest way, but it is the only way to get the perfection demanded to compete with others using such tyres. Therefore I propose that we prepare at once to recommend customers to order wheels with 21" well-base rims, and to have over-size medium pressure tyres on the front (6" 40/50., 5¼" 20 HP) and semi-balloons on the back (6.75" 40/50., and 6" 20 HP.) There are many reasons for this combination, such as - (1) high speed steering wobbles and ease of manoeuvreing at low speeds, (2) it will allow us to slightly increase the deflection of the rear springs at a given load, because the front wheels will be slightly smaller in diameter, and so to keep the car level we can come down about ¾" at the back, unless the lower pressure back tyres run with this amount of extra deflection. If a 40/50 car is so fitted up - i.e. back wheels with 6¾" semi-balloon tyres, and say ¾" more deflection of back road springs, and effective anti-recoil hydraulic dampers on the back also, I feel sure that Sales will agree that they have never had anything to ride so beautifully, and nothing more is possible at the moment. My next point is to take all the weight possible off the front of the car: a specialist should be on this point to help the designers. Then we want an equally smooth, but more powerful non-detonating lighter engine, which is in hand. Mr. Johnson will perhaps distribute this memo. to others if he thinks wise, to keep up the enthusiasm. Such specimen trials cars as I here recommend would be fine. R.{Sir Henry Royce} | ||