All MGBs were fitted with solid (non-ventilated) disc brakes on the front with drum brakes on the rear. The front brake calipers were manufactured by Lockheed and used two pistons per caliper. The brake system on the MGB GT was the same as the roadster with the exception of slightly larger rear brake cylinders. A single-circuit hydraulic system was used before 1968 when dual-circuit (separate front and rear systems) were installed on all MGBs to comply with US regulations. Servo assistance (power brakes) was not standard until 1975. Many modern and contemporary testers have commented on the very heavy brake pedal pressure needed to stop the non-servo-assisted cars.