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).
Vehicle braking, comparing the performance of 4-wheel brakes with rear-wheel only brakes.
| Identifier | ExFiles\Box 73\2\ scan0300 | |
| Date | 26th March 1924 | |
| R.R. 493A (40 H) (BL 42 12-7-23). J.H. D.{John DeLooze - Company Secretary} 49940 EXPERIMENTAL REPORT. Expl. No. 9940 REF: H28/LG26.3.24. to PN.{Mr Northey} from Hs.{Lord Ernest Hives - Chair} c. to EY. S E C R E T. BRAKING. With reference to your PN{Mr Northey}3/DN25.3.24. It is possible to obtain more than double the braking with 4-wheel brakes compared with rear wheel brakes only. The reason for this is that when the brakes are applied the centre of gravity of the car moves forward and there is an increase weight flung on the front wheels which enables more braking to be obtained on the front than on the rear. This varies under different conditions but is roughly 60% front - 40% rear. The stopping distance with any brakes depends entirely upon the road surface. Some of the published records of 4-wheel braking give remarkably high values for co-efficient of friction of the tyre on the road. The value given is sometimes above unity. The best we have been able to obtain on normal roads has been a co-efficient of friction of between .6 and .7. The best records we have obtained on the R-R have been - At 20 M.P.H. 14 ft. " 30 " 40 " " 40 " 75 " Hs.{Lord Ernest Hives - Chair} | ||