The MGB used an all-hydraulic Lockheed braking system throughout its production run, disc brakes at the front and 10-inch drums at the rear. A number of important changes occurred during production that affect parts selection, particularly around the brake hydraulic circuit, servo fitment, and rear wheel cylinder specification.
Front Brakes
All MGBs used Lockheed twin-piston calipers with solid front discs throughout production. Uneven pad wear or pulling to one side under braking usually points to a seized or sluggish caliper piston. New reproduction calipers, exchange reconditioned units, and caliper repair kits are all available, along with a range of brake pads from original specification through to performance ceramic compounds.
For owners seeking a significant step up in stopping power, four-pot vented brake conversions are available.
Rear Brakes
All MGBs used 10-inch rear drums throughout production, with rear brake shoes operated hydraulically via wheel cylinders. The rear brakes are manually adjusted and do not self-adjust, shoes that have not been correctly set leave a disproportionate amount of braking to the front discs. A common selection error is the rear wheel cylinder change point on MGB GTs in 1967, when the GT switched from the roadster’s 0.800-inch bore to a larger 7/8-inch bore unit to correct brake bias for the GT’s greater rear weight. The two cylinders are visually distinguished by the position of the locating pin on the body, a deliberate design feature making it physically impossible to fit the wrong cylinder to the wrong backplate.
Handbrake
The MGB handbrake operates the rear drums via a cable mechanism. There are ten different cable specifications spanning the production run, with variations corresponding to the axle type, wheel type, gearbox type, and bumper type. Late rubber bumper cars from September 1976 onwards incorporate the compensating adjuster within a fixed bar as part of the cable assembly, whereas earlier cars used an entirely flexible cable.
Master Cylinders & Servo
From 1962 to 1967, all MGBs used a single-circuit brake master cylinder. From 1968, export market cars received a dual-circuit system with separate front and rear circuits. UK home market cars did not receive dual-circuit brakes until May 1977, when a new master cylinder with an integral direct-acting inline servo was introduced. A remote brake servo was available as an optional extra from February 1970 and became standard on UK cars from 1973.
Retrofit servo kits are available for cars not originally fitted.
Brake Fluid
DOT 4 glycol-based fluid is the correct specification for any road-driven MGB. Brake fluid is hygroscopic and should be changed at a maximum of five-yearly intervals regardless of mileage. DOT 5 silicone fluid is popular for concours and stored cars as it will not absorb moisture or damage paintwork, but it must never be mixed with glycol fluid and is not a general-purpose replacement for road use.
Brake Lines & Hoses
Rubber brake hoses deteriorate with age regardless of mileage, and internal degradation can cause brakes that apply normally but release slowly. All three flexible hoses should always be replaced as a set. Stainless braided hoses offer improved pedal feel through dimensional stability under pressure. Copper brake pipe sets are available pre-formed with brass unions for both single-circuit and dual-circuit cars.
The MGOC Spares range includes the complete range of MGB brake components, discs, pads, calipers, drums, shoes, wheel cylinders, master cylinders, servos, handbrake cables, brake hoses, copper pipe sets, brake fluid, and performance upgrade kits, supported by expert technical advice for every MGB braking configuration.