On the 100-Six, Girling hydraulics drum brakes were found front and rear, with twin leading shoes at the front. The drums were 11in in diameter, with 21/4in wide linings, and a total frictional area of 188sq in. As the brake and clutch pedals were now of the pendant type, the brake master cylinder was mounted on a bracket above the pedal box, being supplied with fluid from a reservoir on the left-hand vertical support of the bonnet frame. This reservoir also supplied the hydraulic clutch actuation mechanism. The handbrake, found on the right-hand side of the propshaft tunnel, was chrome-plated with a chrome-plated release button and operated a mechanical linkage to the rear brakes. In May 1957, quite early in the BN4 production run, the right-hand seat and carpets were modified to give better clearance for the handbrake. The brake and clutch pedals were square, with studded rubber pads, and curved when seen from the side.
One of the most important modifications on the introduction of the 3000 model in 1959 was that front disc brakes, also made by Girling, were fitted. The discs were 11in in diameter. After about a year in production, the disc brakes had dust covers added to them. Otherwise, the braking system was continued largely without change until August 1961, when on the 3000 Mark II model, from chassis 15104, a Girling vacuum servo unit was offered as an optional extra. This became a standard fitting on the Mark III model in 1963, from chassis 25315.
A final modification occurred only on cars exported to France and the Benelux countries, from chassis 41930 in June 1967, when these cars were fitted with a transparent brake fluid reservoir. This necessitated fitting a new separate fluid reservoir for the clutch.
