Suspension keel

A suspension keel is an extension pylon to the bodywork of single-seat, open wheel racing cars designed with a raised nose cone, to allow the lower suspension arms to be attached to the car approximately parallel to the road surface. In recent years the placing and design of a suspension keel, or the lack of such, has been one of the few distinct variables in Formula One chassis design.

Traditional low nose cone designs (e.g. the McLaren MP4/4) allow the lower suspension arms to be directly attached to the main structural members of the car. However, since the move to high nose cone designs - which allow better use of airflow underneath the car, and to a lesser extent the front wing - location of these lower arms has proven problematic. For ideal suspension geometry, and hence maximum mechanical grip, the lower arms should be long and near parallel with the road. As there is no longer any structural bodywork in these low positions, extensions were developed to allow the suspension to be mounted with correct geometry. Since the advent of high nose designs in the early 1990s, pioneered on the Tyrrell 019 Formula One car, three major keel designs have emerged to solve this problem:

One limitation of any keel design is that, while the keel influence may vary, the suspension linkages themselves still disrupt the underbody airflow. This problem was exacerbated when the FIA introduced rule changes in 2005 that forced teams to mount their front wing in a more elevated position. In response to this, many F1 teams have developed zero-keel chassis designs. Here the keel is removed entirely, and the suspension is mounted directly to the chassis. As the nose cone is in a raised position, this entails that the suspension arms take a distinctly inclined angle with respect to the road surface, reducing suspension efficiency. However, with continued restrictions to aerodynamic downforce through the use of aerofoil wings, and the lighter V8 engines specified from 2006 onwards causing weight distribution to shift forward, many designers apparently consider this drawback to be less significant than the concomitant increase in venturi downforce generated underneath the car; except for Renault and Red Bull, all of the teams in the 2007 Formula One World Championship used a zero-keel design.

...
Wikipedia