By mid-1967, the Cooper T81 had slipped behind the newer cars of the leading teams. A new chassis was built for Cooper's lead driver Jochen Rindt, making its debut at the British Grand Prix. The T86 was narrower, lower, and lighter than its predecessor, fabricated from Elektron alloys. A distinctive bump around the gear lever gave the driver additional space when changing gear, a feature that went on to appear on many single-seater cars through the 1970s. The new chassis was approximately 112 lb lighter than the T81, though it was still considered overweight largely because of its ageing Maserati V12 engine.
The car was found to become light at the front at high speeds. Ahead of the Italian Grand Prix, this was addressed by fitting a small spoiler on the nose — an innovative solution for the era. Jacky Ickx drove the T86 at Watkins Glen, and Ludovico Scarfiotti gave it its final works outing in the first race of 1968.
The car subsequently passed to privateer Colin Crabbe, who fielded Vic Elford in it for the 1969 International Trophy at a team called Antique Automobiles. Neil Corner also drove it at the non-championship Madrid Grand Prix. Elford returned for the Monaco Grand Prix, where the car qualified last and finished last of the classified runners — six laps down in seventh place. That race marked the last time a Cooper competed in a championship Grand Prix.
For the 1968 season a B-specification T86 was developed to accept a BRM V12 engine in place of the ageing Maserati unit, making its debut at the second round of the season in Spain. Two cars were initially constructed, with a third built after Brian Redman crashed at Spa. The BRM unit installed was a less powerful sportscar derivative of an engine that was already among the heaviest on the grid.
Despite these limitations, the T86B delivered some respectable results early in the season, finishing third and fourth in both Spain and Monaco — aided significantly by the unreliability afflicting other cars. However, the car faded toward the season's end. The Mexican Grand Prix served as the final Formula One race for any works Cooper entry, as the team concluded it could not fund a 1969 campaign and auctioned off its remaining T86B chassis. One of those cars was later acquired by Martin Brain, who raced it in British hillclimb and club events before a fatal accident at a Silverstone Formula Libre race in 1970 when the car left the track and overturned.
A third T86 variant was built in 1968 to accept a 3.0-litre Alfa Romeo V8 engine of the type used in the Tipo 33 sportscar. Cooper hoped the Alfa unit might become a future alternative to the BRM. Lucien Bianchi was entered in the car at Brands Hatch and Monza but did not participate in either event, with Alfa Romeo withdrawing support after testing revealed the V8 was badly underpowered and subsequent development work failed on the test bench.
Alfa Romeo eventually entered Formula One with the V8 via McLaren in 1970 and March in 1971. The T86C chassis was later converted to Formula 5000 specification with a 5-litre Ford V8 and campaigned in 11 events during the 1970 Guards European Formula 5000 Championship by driver Fred Place, without significant success. The car was subsequently stolen but the chassis was eventually recovered and later restored to its original configuration with a comparable Alfa Romeo V8, and has since appeared regularly in historic racing.
The Cooper T86 in its various forms brought an end to one of the defining stories in Formula One's first decade. Cooper had helped pioneer the rear-engined layout that became universal in Formula One, and had won the Drivers' Championship with Jack Brabham in 1959 and 1960. The T86 marked the conclusion of that journey, with Cooper unable to find the resources to compete into 1969. Its final championship appearance at Monaco in 1969 with Elford at the wheel — last on the grid, last at the flag — was a poignant footnote to a once-dominant constructor.