Hydraulic braking systems for vehicles

In a wheel mounted vehicle having a high centre of gravity hydraulically-operated brakes are provided for braking at least one wheel on each side of said vehicle, and an hydraulic braking system is incorporated for operating said brakes, wherein said braking system comprises hydraulic actuators for applying said brakes, a pedal-operated hydraulic master cylinder assembly having first and second modes of operation, which in its first mode supplies hydraulic fluid to said actuators simultaneously for pure vehicle retardation and in its second mode supplies hydraulic fluid to said actuators independently to assist steering, and inertia-controlled valve means interposed between said master cylinder assembly and said actuators, said inertia controlled valve means being normally open to permit the flow of hydraulic fluid between said master cylinder assembly and said actuators for the brakes on both sides of said vehicle but closing when subjected to a vehicle deceleration exceeding a predetermined value whereby the pressure of fluid from said master cylinder assembly to said actuators is reduced by closure of said valve means at least when said brakes are applied simultaneously for pure vehicle retardation and said vehicle deceleration has exceeded said predetermined value, said predetermined value exceeding that to which said vehicle can be subjected in said second mode of operation of said master cylinder assembly.