The first appearance of aerodynamic devices on rally cars is dated in mid-sixties when Porsche presented the 904 GTS model, designed by Butzi Porsche. The car included a small spoiler in the back of the car, integrated into the bodywork, which was done with Pantal, a glass fiber from BASF.
E.Böhringer/R.Wütherich, Porsche 904 GTS, Rally Monte Carlo 1965 (2nd)
In 1970 Simca started to compete with the CG Coupe model with a rear, bigger spoiler. The car was developed by Bernard Boyer (Matra).
G. Larrousse / B. Gelin, Simca CG Coupé 2.2, Criterium de Cevennes, 1970 (1st)
B.Fiorentino/B.Gelin, Simca CG Coupe, Lyon-Charbonnières 1973 (1st)
Also, Ford presented his new car devoted to rallies in 1970 Brussels Show Car designed by Len Bailey. It was the GT 70 model, with also a rear spoiler.
F. Mazet/J.Todt, Ford GT 70, Tour de France 1971 (retired)
Unfortunately, FIA rules for the new World Rally Championship to start in 1973 required production of 500 cars to get homologation as group 4, which forced Simca and Ford to renounce.
In 1972 Porsche launched the 911 Carrera RS 2.7 model with a more developed rear spoiler, which made the car was known as ‘duck tail’. It was the result of an extensive work in the wind tunnel.
Porsche 911 Carrera RS 2.7 in the wind tunnel. The rear of the car is fitted with tuft (made of paper, wool or any other light material), to help visualize flow in this area. The car is over suspended bars, in order to measure lift/downforce on different axes.
Use of this spoiler resulted in a reduction in load at the rear part of the car estimated at 90 kg. It helped improving car stability as well as moving back the car aerodynamic pressure center.
The car took part in many rallies of the new-born World Rally Championship since 1973.
B. Waldegaard/H. Thorszelius, Porsche 911 Carrera RS 2.7, Safari Rally 1974 (2nd)
Lancia proposal to renew victory after successful Lancia Fulvia was the Stratos, designed by Bertone, which was first presented at Turin in 1971. First units did not have any aerodynamic device. First spoiler prototype appeared in 1973 in the Tour de France.
S. Munari/M.Mannucci, Lancia Stratos HF, Tour de France 1973 (1st)
It was not until 1975 Safari Rally when Stratos was equipped with the definitive spoiler, as well as the so-called air deviator, according to FIA Homologation Form from November 1974 (here), which consisted in a thin blade over the rear part of the roof, designed to channel air into the rear spoiler.
S.Munari/L.Drews, Lancia Stratos HF, Safari Rally 1975 (2nd)
R. Pinto / A.Bernacchini, Lancia Stratos, Monte Carlo Rally 1977 (retired)
History continues in the 70’s.