The calculation of the effective circumference and diameter for a 20 HP car's balloon tyre.
| Identifier | ExFiles\Box 53\3\ Scan049 | |
| Date | 5th April 1927 guessed | |
| A.J.L. Please <s>file</s> <s>Could you let me have the effective rolling dia of the 33 x 5 1/4 20 H.P. balloon tyres at 35 lbs / □"</s> 20 H.P. 33 x 5 1/4 tyres 35 LBS / □" Effective circumference = 96.4375" .. diameter = 30.70" (New type; weight of rear of car on which tyre was fitted = 1 TON Weight of N.S. rear of car, side on which wheel was fitted for measurement = 10 cwt) | ||
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).