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).
Axle ratios and tyre sizes for the 20 HP model.
| Identifier | ExFiles\Box 102\4\ scan0031 | |
| Date | 23th May 1928 | |
| Y5350 To CWB. from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}5/LG23.5.28. X5350 X4050 20 HP. AXLE RATIOS. Replying to CWB8/GM22.5.28. We have already given you with full particulars of all the tyres used on the cars in our Hs{Lord Ernest Hives - Chair}/Rml/LG3.12.27. This list includes the 32 X 45 high pressure straight sided tyre the effective circumference of which is 101.25". With reference to the 20" rim and 6" tyre. Having run 10,000 miles on a lower geared axle and on 6" tyres 21" rims, and having standardised both, we think it would hardly be worth while repeating the procedure on the 20" rim with another tyre in order to obtain the same result. As you will see from the memo. quoted above, we are already dealing with three types of tyre on the 40/50 and on the 20 HP. We should be very reluctant to depart from the 21" rim which is common to 40/50 and 20 HP. and additionally to have another tyre size. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||