The front and rear suspension had double wishbones and coil springs but with revised geometry to correct the T60's tendency to nose-dive under braking.

[1] Cooper raced the T66 for the first time at the 1963 Monaco Grand Prix, driven by Bruce McLaren and Tony Maggs.

He followed up with second at a rain-soaked Spa, but the rest of the season was less encouraging, McLaren managing no better than another third place at Monza.

Also for 1963, Rob Walker purchased a T66 for Jo Bonnier to drive but problems delayed its race debut until the British Grand Prix.

[2] The Walker car continued into 1964, but mostly as a spare, and its last race was at the German Grand Prix, driven by Edgar Barth.