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).
Comparison of speeds with different tyre pressures on a 6-EX car.
| Identifier | ExFiles\Box 39\2\ Scan161 | |
| Date | 2nd May 1923 | |
| X3538 COMPARISON OF SPEEDS WITH DIFFERENT TYRE PRESSURES. Tests carried out on 6-EX Car. Dunlop cord tyres 33 X 5. Road - smooth tarmacadam. No wind - dry. Test 1. 80 lbs. per sq.in. in tyres. Start - To Shardlow - M.P.H. 10 43 55 60.5 } 43.5 secs 10 43 55 60.0 } 43 secs. From Shardlow 10 40 50 58 } 43 secs. 10 40 50 58 } 43 secs. Test 2. 40 lbs. per sq.in. in tyres. To Shardlow - 10 43 55 60 } 42.8 secs. 10 44 55.5 60.76 } 43.8 secs. 10 43.5 55.5 60.75 } 43.2 secs. From Shardlow 10 40.5 50 57 } 43.5 secs. 10 40.5 55.5 58 } 42.8 | ||