The BT49 family had debuted in 1979 as a rapid replacement for the team's troubled Alfa Romeo-engined BT48. Designed in only six weeks, the BT49 used the reliable Ford Cosworth DFV engine and ground-effect aerodynamics — air accelerated under the specially shaped underbody creating downforce without the drag associated with conventional wings. Niki Lauda abruptly quit racing during the car's debut weekend, leaving Piquet to develop the car through 1979 and 1980. The BT49 and an updated BT49C ran concurrently through 1981, with five BT49C chassis built new and two earlier cars converted to the specification.
For 1981, the FIA banned sliding skirts and imposed a minimum ride height of 60 millimetres to limit ground effect. The BT49C regained front wings to compensate for the lost downforce. More significantly, Murray devised a hydropneumatic suspension system using soft air springs. When the car was stationary and could be measured by scrutineers, the system held the car at the legal 60mm height. Once moving, aerodynamic downforce compressed the air and the car settled to a much lower effective ride height, substantially increasing ground-effect downforce. Because skirts were now fixed rather than sliding, the suspension had to be extremely stiff to maintain consistent sealing around the car's sides; by the end of the season, total suspension travel was only 38mm, roughly half of which came from tyre deflection.
A lightweight qualifying chassis was produced for the BT49C, featuring a smaller fuel tank and the carbon-carbon reinforced brake discs and pads that Brabham had pioneered in Formula One in 1976.
The car used the Ford Cosworth DFV V8 engine, producing approximately 500 brake horsepower at around 11,000 rpm. Cosworth supplied Brabham with "evolution" DFV units featuring a marginally shorter stroke and higher-revving specification, effectively making Piquet the favoured works Cosworth runner after Williams chose to sub-contract engine development internally from mid-1980.
The season opened at Long Beach, where the BT49C was introduced. Other teams were surprised by the car's speed; Murray had expected competitors to immediately exploit the same compliance in the ride-height rule, but no rival had done so. Early races were complicated by the hydropneumatic system repeatedly jamming, forcing the team to race with conventional suspension while continuing to develop the device. By the Argentine and San Marino Grands Prix the system worked consistently, and the car took pole positions and race wins.
Frank Williams protested the car at Argentina, objecting that the flexible fixed skirts replicated the effect of a banned sliding skirt. Scrutineers rejected Brabham's skirts for the following race; the team sourced stiffer material from another team and Piquet won anyway. As the season progressed, rivals developed their own ride-height lowering systems — a front spring assembly was stolen from the Brabham garage in Argentina — though a FISA clarification allowed many teams to lower their cars at the push of a switch, which Murray considered inferior to Brabham's integrated engineering approach.
The BT49Cs also faced a tyre disruption. Goodyear temporarily withdrew from Formula One and the team had to adapt to Michelin's radial tyres for part of the season, with some cost to competitiveness. Despite very stiff suspension putting components under extreme strain, Piquet completed 10 of 15 races with only one mechanical failure. He clinched the championship at the Caesars Palace Grand Prix in Las Vegas, finishing fifth to take the title from Reutemann by a single point.
The BT49C's hydropneumatic suspension was one of the more ingenious regulatory exploits in Formula One's technical history. The concept — using the aerodynamic load itself to lower the car below nominal ride height — inspired imitators and eventually precipitated further rule clarification. The car demonstrated that compliance, correctly engineered, could be more powerful than outright speed. BT49 variants have competed regularly in FIA Historic Formula One Championship events since 1995, and the BT49C remains a sought-after car in historic motorsport.