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).
Testing and performance of unequalized rear brakes on a Bentley.
| Identifier | ExFiles\Box 85\1\ scan0001 | |
| Date | 8th January 1936 | |
| To E.{Mr Elliott - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to E/Tsn. x206 Hs{Lord Ernest Hives - Chair}/AFM.{Anthony F. Martindale}11/KW.8.1.36. Bentley with Unequalized Rear Brakes. With reference to memo. E/Tsn.5/MN.18.12.35, dealing with the legal requirements for cars fitted with only one set of brake shoes in the rear brake drums. We have locked the rear equalizer of 3-B-IV solid, and are running this car about to see if the brakes wear equally or not. We have tried the car on the road with one rear brake adjusted back and the car is perfectly controllable. At the same time the decrease in braking power is quite noticeable. We are making an apparatus to measure this. With the hand brake working on one rear wheel only, with a coefficient of friction of .5 between tyre and road, it would be impossible for the driver and sole occupant of a Bentley when descending a hill of slope 1 in 7.5 to get out of his car even for an instant, whereas if the rear brakes were equalized he could do so on a slope of 1 in 4.5. We think this is a disadvantage. If an unequalized system of rear brakes is used, we regard it as most important for the sponge in the linkage to each rear wheel to be the same; otherwise the brakes will never be as good as possible and one set of linings will always wear out first. We would like to refute the suggestion that unequalized rear brakes are necessary in order to keep the system simple, and at the same time comply with the law. Whereas with equalized rear brakes all that is necessary is a stop to prevent excessive travel of the rear brakes in case of failure, with an unequalized system a somewhat complex system of sponge equalization is necessary if the efficiency of Rolls-Royce brakes is to be maintained. Hs{Lord Ernest Hives - Chair}/A.F. Martindale. | ||