Lotus built the Type 51, Type 51A, and Type 51R during the 1967 and 1968 seasons. The cars had multi-tubular space-frame chassis which was suspended in place by double wishbones and coil spring/damper units in the front and reversed lower wishbones, upper links, twin radius rods and coil spring/damper units in the rear. The Type 51A was introduced in 1968 and was very similar to the Type 51, with a few modifications. There was only one Type 51R ever created. It was shown at the 1968 Racing Car Show as a publicity stunt. It was adorned in a 'flower-power' color scheme that was vibrant, flamboyant, and daring.
There were differences between the Lotus 51A, B, and C models. The 51A models did not have mounting for a dry-sump system; the 51Bs were given an updated and improved rear suspension system and the Lotus 51C models had a Hewland transaxle.
The Type 51 Series did very well in Formula Ford competition and this helped increase demand for the vehicles. In total, around 218 examples were produced.