The brake disc conversion kit converts an MGA 1500 from its original Lockheed drum brake specification at the front to a disc brake installation, effectively upgrading the 1500 to the factory brake specification of the later 1600 and 1600 Mk II. Two conversion routes are available: the standard conversion kit matched to the car's wheel type (steel or wire), and a premium aluminium 4-pot vented kit offering significantly higher braking performance for harder-used cars.
Standard disc conversion kit, steel wheel and wire wheel
The standard conversion kit is stocked in two variants matched to the car's wheel type. The steel wheel kit suits MGA 1500 cars originally fitted with the bolt-on steel disc wheels and four-stud disc-wheel hubs. The wire wheel kit suits 1500 cars originally fitted with Dunlop 48-spoke wire wheels and splined centre-lock hubs. Both kits provide the front disc brake installation matching the factory architecture of the later 1600; the difference between them lies in the hub specification supplied with each kit, which must match the wheel type fitted to the car.
The standard kit replaces the 1500's original Lockheed 10-inch drum brakes, two wheel cylinders and leading shoes at the front with discs, calipers and friction pads. The existing combined brake-and-clutch master cylinder can be retained, no master cylinder change is required for the conversion. The rear brakes remain as drums whether the car is converted at the front or not.
Aluminium 4-pot vented brake kit
The Aluminium 4-Pot Vented Brake Kit is a significantly higher-specification upgrade than the standard disc conversion. Four-pot calipers clamp the disc from both sides with four individual pistons per caliper, giving more even pad pressure and substantially greater clamping force than the single- or two-pot calipers used on the standard kit. The discs are vented, internal vanes between the disc faces that allow cooling air to flow through the disc under rotation, dissipating heat far more effectively than the solid discs used on the standard kit. The aluminium caliper bodies are significantly lighter than conventional cast-iron calipers, reducing unsprung weight at the front axle.
The 4-pot vented kit is stocked for MGA 1500 cars with wire wheels. The kit is aimed at MGAs used on track days, at hill-climb events, or for fast-road use where the additional thermal capacity and clamping force justify the significant upgrade over the standard disc conversion.
Scope, 1500 only
Both conversion routes, standard and 4-pot, apply to MGA 1500 cars only. The 1600 and 1600 Mk II already have Lockheed front disc brakes from the factory and do not need converting. The Twin Cam and De Luxe use 11-inch Dunlop disc brakes as their factory specification and do not use Lockheed-pattern conversion kits. For the 1600 and 1600 Mk II, service-parts upgrade routes (uprated pads, improved discs) are covered under the Uprated Brake Discs & Pads node.
For the Twin Cam and De Luxe, the factory Dunlop disc installation is the correct specification.
Concours vs. driving considerations
For a 1500 being restored to concours standards or to factory-original specification, the original Lockheed drum brake arrangement should be retained, the disc conversion is not a factory option and is visible as a non-original modification under inspection. For a 1500 used regularly on the road, the standard disc conversion is a well-established upgrade route. For a 1500 used at track events or in competitive driving, the 4-pot vented kit gives a much larger margin of thermal capacity than either the standard conversion or the factory 1600 disc specification.
Ordering considerations
Ordering starts with the car being a 1500 (conversion kits are not applicable to other MGA variants), and with confirmation of the wheel type fitted, steel disc or wire wheel, so the matched hubs are supplied in the kit. The standard disc conversion kit is available in both wheel-type variants; the 4-pot vented kit is currently stocked in the wire wheel specification only.
Owners of 1500 cars with steel wheels wanting to move to the 4-pot specification would need to consult MGOC on compatibility of a wire-wheel-fitment kit with their car's current wheel and hub arrangement. Both conversions install onto the existing 1500 front suspension without structural modifications; once fitted, modern DOT-specification brake fluid is compatible with the system after proper bleeding and flushing.