No fewer than three different braking systems were fitted to MGAs across the model's production run, which makes brake parts selection one of the most variant-critical areas of the car. The 1500 uses Lockheed drum brakes at all four wheels. The Twin Cam and De Luxe use 11-inch Dunlop disc brakes at all four wheels. The 1600 and 1600 Mk II use Lockheed front disc brakes with rear drums.
The three systems share almost no common parts, and the front hubs, stub axles and steering knuckles also differ between them (covered under the Stub Axles & Hubs node within Suspension & Steering). Identifying the correct system for the car, and, within each system, the relevant chassis-number breakpoints for production changes, is the first step in ordering any brake component. This section covers all MGA brake parts under seven sub-categories: front brakes, rear brakes, handbrake, brake lines, master cylinder and pedal box, brake fluid, and brake-related upgrades.
MGA 1500, Lockheed all-drum brakes
The 1500 runs Lockheed drum brakes on all four wheels. The drums are 10 inches in diameter and 1¾ inches wide at both front and rear, and are painted black. The front brakes use two wheel cylinders per drum giving two leading shoes, a configuration chosen for improved stopping power, since leading shoes are self-energising under the wheel's rotation. The rear brakes use a single wheel cylinder per drum with one leading and one trailing shoe.
Original lining specification is Ferodo DM13, size 9.6 x 1.75 inches, giving a total lining area of 67.2 square inches at both front and rear. A combined brake and clutch hydraulic master cylinder with integral supply tank sits on the horizontal shelf behind the engine above the footwell; the master cylinder body is left as an unpainted casting with the supply tank cover in natural metal finish. Pendant pedals sit directly below the master cylinder, with the pedal arms passing through a one-piece black rubber fume excluder. Pedal design was modified at car/chassis 58713.
Rear brake pipe connections were standardised to UNF threads at car/chassis 27989 (disc-wheeled cars) and 28540 (wire-wheeled cars); the banjo connection to the rear wheel cylinders was changed from a straight to a right-angle type at car/chassis 22741.
Twin Cam and De Luxe, Dunlop all-disc brakes
The Twin Cam and De Luxe use 11-inch Dunlop disc brakes at all four wheels, the only MGA variants with four-wheel disc brakes. These cars have separate brake and clutch master cylinders, and the brake pipe runs differ from the pushrod cars. The disc brake calipers were modified at approximately car/chassis 836. At car/chassis 997, the master cylinder box was modified to avoid the fitting of a taper packing between master cylinder and box.
The De Luxe uses a slightly modified Twin Cam master cylinder, and a service kit was made available during production to convert an original Twin Cam master cylinder to the later specification. The factory-recommended brake fluid for these cars is Wakefield Crimson brake fluid (later superseded by Dunlop disc brake fluid), or alternatively any brake fluid to specification SAE70.R1 or SAE70.R3. Full fluid coverage is under the Clutch & Brake Fluid node (shared Castrol range). The handbrake operates on special pad carriers attached to the rear disc calipers, an arrangement the Identification Guide describes as "not terribly effective and troublesome to set up".
This is a known characteristic of the Twin Cam and De Luxe brake system rather than a fault of individual cars.
1600 and 1600 Mk II, Lockheed front disc, rear drum
The 1600 and 1600 Mk II (other than De Luxe models, which inherit the Twin Cam brake architecture) use 11-inch Lockheed disc brakes at the front with 10-inch drum brakes at the rear. The front disc studs were replaced by bolts at car/chassis 69505 (disc-wheeled cars) and 70276 (wire-wheeled cars). Improved brake pads were introduced at car/chassis 78106, and the new pads are recommended for all replacements on earlier cars. On the 1600 Mk II, dust covers for the brake discs were introduced from car/chassis 102589.
The rear drum brakes on the 1600 and 1600 Mk II are the same dimensions as the 1500 drums but with later DON24 linings, size 9.63 x 1.7 inches. From the start of 1600 production, the brake pedal arm was redesigned and the master cylinder received a much deeper cover for the supply tank. The hydraulic pipe runs and the handbrake mechanism are largely carried over from the 1500 and were not modified during 1600 and 1600 Mk II production.
Handbrake, common to all variants
The handbrake is a fly-off type fitted on the right-hand side of the propeller shaft tunnel, sitting horizontally and out of the way in the off position. It activates the rear brakes by cable.