Like its immediate predecessors in the Brabham lineage, the BT54 distributed most of its weight towards the rear of the car to help traction. With FISA having banned the winglet arrangements pioneered by Ferrari in 1983, Murray placed small auxiliary wings on the outer rear edges of the sidepods instead. The decision to sign with Pirelli after Michelin's withdrawal from Formula One at the end of 1984 — rather than switch to Goodyear alongside most rivals — would prove decisive to the season's outcome.
Pre-season testing was conducted by two-time world champion Nelson Piquet in the southern hemisphere summer at Kyalami and Jacarepaguá, completing the equivalent of roughly 75 race distances. The warm conditions suited the Pirelli rubber, masking a critical weakness: the tyres took far longer than Goodyears to reach working temperature in cool conditions, generating severe understeer — a problem compounded by the BT54's rearward weight bias.
Once the European calendar began, the tyre deficit became apparent. The car excelled on high-speed circuits where the BMW engine's raw power compensated: Marc Surer set the fastest speed trap of the season at Paul Ricard during qualifying, with the BT54 clocking 335 km/h on the Mistral Straight. Both Piquet and Surer reached 332 km/h at Kyalami's front straight.
The one occasion where track, conditions and machinery aligned was the French Grand Prix at Paul Ricard, run in exceptional heat. Piquet qualified fifth and converted the conditions into Brabham's only victory of the year. On slow street circuits — Monaco, Detroit, and Adelaide — the car was uncompetitive; Piquet never qualified higher than tenth nor finished higher than fifth at any of the three.
At Zandvoort, Piquet took his only pole position of the season, but stalled on the formation lap and lost more than two-thirds of a lap before receiving a push-start. At Brands Hatch for the European Grand Prix, a collision with Keke Rosberg's stalled Williams on lap seven ended Piquet's race; Surer ran as high as second before retiring thirteen laps from the finish with a fiery engine failure.
The team's three drivers across the season — Piquet, François Hesnault, and Marc Surer, who replaced Hesnault from the Canadian Grand Prix onward — accumulated 26 points, placing Brabham fifth in the Constructors' Championship.
The BT54 was replaced for 1986 by the radical low-line Brabham BT55, though the older car was pressed back into service for the 1986 British Grand Prix at Brands Hatch when the BT55 failed to produce results. The 1985 season also marked the end of Nelson Piquet's seven-year association with Brabham: after two world championships and twelve wins with the team, the Brazilian signed with Williams-Honda for 1986, going on to win seven races over two seasons and claim his third world title in 1987.
The BT54 represents the final expression of Gordon Murray's rear-weight philosophy at Brabham and the last car Piquet drove for the team that made his name. Its season illustrates the amplified importance of tyre choice in the turbocharged era: a car capable of 335 km/h on a straight could be neutralised by rubber that simply would not warm up in ordinary European conditions. The BMW engine's sheer power kept Brabham relevant on fast circuits, but without a tyre partner to match its rivals the team's decline from championship contention was confirmed by season's end.