 Against the trend set by the Lotus 21 in 1961 , the BT19 's suspension , which controls the relative motion of the chassis and the wheels , is outboard all round . That is , the bulky springs and dampers are mounted in the space between the wheels and the bodywork , where they interfere with the airflow and increase unwanted aerodynamic drag . Tauranac persisted with this apparently conservative approach based on wind tunnel tests he had carried out in the early 1960s , which indicated that a more complicated inboard design , with the springs and dampers concealed under the bodywork , would provide only a 2 % improvement in drag . He judged the extra time needed to set up an inboard design at the racetrack to outweigh this small improvement . At the front the suspension consists of unequal length , non @-@ parallel double wishbones . The front uprights , the solid components upon which the wheels and brakes are mounted , were modified from the Alford & Alder units used on the British Triumph Herald saloon . The rear suspension is formed by a single top link , a reversed lower wishbone and two radius rods locating cast magnesium alloy uprights . Wheels were initially 13 inches ( 330 mm ) in diameter , but soon upgraded to 15 in ( 380 mm ) at the rear , and later still 15 in at the front as well . These increases enabled the use of larger , more powerful brakes . Steel disc brakes are used on all four wheels and were of 10 @.@ 5 in ( 270 mm ) diameter for the smaller wheels and 11 in ( 280 mm ) for the larger ones . The car ran on treaded Goodyear tyres throughout its racing career . 
