The Lotus 49 had debuted at Zandvoort in 1967 with Jim Clark winning on the car's very first outing. Its defining engineering feature was the use of the DFV engine as a structural load-bearing member bolted directly to the monocoque, with the gearbox and rear suspension attached at the other end — a configuration that virtually every subsequent Formula One car would adopt. The 49B introduced wings mounted directly to the wheel hubs on slender struts, standing several feet above the bodywork to operate in clean air. The concept followed Ferrari's introduction of strutted wings in Formula One, but the Lotus application was among the most prominent examples of the technology. After several wing failures caused dangerous accidents the high wings were banned, and teams were required to mount wings directly to the car's bodywork.
The 49B arrived at a moment of profound change for Team Lotus. Jim Clark, who had won the opening race of 1968 in South Africa in the original 49, was killed at Hockenheim in an unrelated Formula Two race in April. Graham Hill became team leader and drove the 49B to his second World Championship, winning three Grands Prix including the Monaco Grand Prix — the fourth of his five victories at that circuit.
Jo Siffert drove a 49B entered by Rob Walker to victory at the 1968 British Grand Prix at Brands Hatch. That result is historically notable as the last time a car entered by a genuine privateer — not a works team — won a championship Formula One race.
Jochen Rindt took the 49B to his first Formula One victory at Watkins Glen in 1969. The car was intended to be replaced mid-1969 by the experimental four-wheel-drive Lotus 63, but when that car proved a failure an improved 49C was pressed into service. Rindt drove the type to its final victory at the 1970 Monaco Grand Prix. The Lotus 72 eventually took over as the team's primary challenger through the 1970 season.
Fitted with a 2.5-litre Cosworth DFW variant of the DFV, the 49 and 49B also competed in the Australian and New Zealand Tasman Series. Jim Clark won the 1968 Tasman Series, taking four of the eight rounds including the Australian Grand Prix at Sandown. Jochen Rindt replaced Clark for 1969 but finished second in the series behind Chris Amon's Ferrari.
Twelve Lotus 49s were built in total; seven survive. Chassis R3, driven by Graham Hill and later sold to privateer John Love, is the only surviving example of the original 1967 specification and is on display at the National Motor Museum in Hampshire, England. The car appears in numerous racing video games including iRacing, Assetto Corsa, and Forza Motorsport. The DFV engine the 49 introduced went on to power most of the Formula One grid through the 1970s, making the design one of the most influential in the sport's history.