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).
Trend by US tyre makers to increase tyre sizes for the 40/50 HP model, outlining the benefits.
| Identifier | WestWitteringFiles\J\December1922\ Scan54 | |
| Date | 12th December 1922 | |
| To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair} c.c. to CJ. c.c. to E.{Mr Elliott - Chief Engineer} c.c. to EY. c.c. to Dn. ORIGINAL. Hs{Lord Ernest Hives - Chair}2/LG2.12.22. TYRES FOR 40/50 HP. X4565 We have heard from OY. that there is a movement amongst the Tyre makers in U.S.A. to increase the size of the tyres allround. The 33 X 5 tyre which is the one we are using on the 40/50, will be replaced by a tyre 32 X 6. The rolling diameter of the 32 X 6 tyre will be the same as the 33 X 5. The advantage claimed is, greater life than the present cords. With the riding qualities of the old canvas tyres the rolling resistance is said to be scarcely increased. The tyre pressure can be reduced from 60 lbs. to 40 lbs. Finally, the big gain is said to be increased traction co-efficient and elimination of brake jaggers in the rear axle. By means of the larger tyres and lower tyre pressures, American manufacturers hope to delay or defeat the 4-wheel brake movement. The larger tyre also enables the wheel maker to make a stronger wheel for latteral blows. Upon receipt of this information we wrote to the Development Dept. of the Dunlop Co. and asked them whether they were contemplating making similar tyres. Attached herewith is their reply. In our opinion is that we should test these larger tyres. We are certain that there will be an insistent demand for lower and still lower tyre pressures. (Hs.{Lord Ernest Hives - Chair}) | ||