Ferrari: Rear Dual Rate Anti Roll Bar

Ferrari rear suspension package: copyright- Liubomir Asenov

When comparing the fortunes of the three leading teams, one stand out feature has been Ferraris kindness to its tyres and its great traction. Although both these traits are hugely complex and achieved by a variety of factors, we have been able to identify a solution in Ferraris rear suspension that may be providing some of this mechanical grip. As one of the few leading teams to retain pushrod suspension in 2011, Ferrari have at least given a chance to see the clever mechanical set up at the of the car. We have already discussed the relative merits of pushrod Vs Pullrod and looked at the rear end packaging of the Ferrari (see the links at the end of this article). But what this detailed shot by Liubomir Asenov shows us, is the clever arrangement of the rear Anti Roll Bar (ARB). Ferrari have developed sprung drop links to create a dual rate ARB, which gives the team the advantage of soft roll control for low speed grip and stiff roll rates for high speed aero grip.

A typical Anti Roll Bar. copyright: Craig Scarborough

An Anti Roll Bar (ARB) is a spring that helps the chassis resist roll when cornering. Typically in a racecar this is a relatively simple “U” shaped arrangement, with levers acting on a torsion bar. Drop links lead from the rocker to the ARB. When the car rolls one rocker goes down and the other goes up. The links twist the ARB, which in turn provides the spring effect to resist the cars roll. A stiff rear ARB will be good for maintaining the underfloors attitude to the track, in order for the diffuser to work at its best. However at lower speed, a softer ARB will aid grip by allowing each tyre to maximise its contact with the track. Clearly some tracks will favour aero over mechanical grip, but laptime gains be found if the car can improve both aero and mechanical grip.

What Ferrari has done is to replace the drop links that lead from the suspension rocker to the ARB levers with small coil springs. Now when the car rolls, the softer coil spring compress first, these provide a soft initial ARB rate, which provides good mechanical grip. Then as their movement is taken up, the coil springs act like solid links to the ARB and the stiffer main ARB provides the tighter roll control to aid the underbodies aerodynamics.

This solution appears to be unique to Ferrari in F1, but is a known solution in other race series.
Andrew Thorby (Designer for Panoz, Lister, McLaren MP4-12c GT3) pointed out to me that Lola is known to have used this solution in some of their cars, using either coil springs or belleville springs. He also pointed out that although small; these Ferrari coils springs are mounted quite high up, over what is already a relatively high suspension package, thus upsetting the cars Centre of Gravity slightly. Other teams achieve similar variable rate ARBs with the geometry of the drop links and levers. Whether pushrod or Pullrod, any team could conceivably employ these spring links to provide this variable roll rate.

Analysis of Ferraris rear end packaging
http://scarbsf1.wordpress.com/2011/03/23/ferrari-rear-end-exhaust-and-drs-mechanism/

Analysis of pushrod versus pullrod
http://scarbsf1.wordpress.com/2010/10/10/red-bull-pull-rod-suspension-what-is-looks-like-how-it-benefits-aerodynamics/

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