It’s not often that we get to experience a new and completely novel piece of automotive technology for the first time. But that’s what Lamborghini seems to have created with its Active Wheel Carrier, which we have now sampled in prototype form. The system itself is both clever and complex, but the basic purpose is simple: to give real-time control of camber and toe alignment settings while a car is moving.
According to Rouven Mohr, Lamborghini’s chief technical officer, this is one of the final frontiers of vehicle dynamics. Suspension geometry is usually based around a set of compromises, with the loads created by a car in motion inevitably negatively affecting at least some of these. And the alignment settings that are right for the track will cause premature tire wear on the street, which is why many high-performance cars have track-alignment settings and necessitate switching back and forth. Gaining active control in two different planes—toe being the angle of the rotating wheel relative to the direction of travel, and camber its side-on angle relative to the ground—means that many of these compromises can be eliminated. The results, based on our drive in a Lamborghini Huracán development mule at Porsche’s Nardò test track in Italy, are deeply impressive.
The idea itself is not new, and Mohr admits that work on it was being done at fellow VW sibling Audi when he previously worked there. But as well as the hardware required to move the wheel in two planes, the challenge is creating a control system capable of doing so quickly and accurately enough to allow the benefits to be exploited. This is an area in which Lamborghini is leading the way.
The system works exclusively on each of the Huracán prototype’s rear wheels. Active toe control is, in essence, a rear-steering system. We’ve had those before, of course—but this one can also move the wheels between toe-in, where the leading edges point very slightly toward each other, and toe-out, where they do the opposite. In very general terms, toe-out makes a car more reactive and keener to turn, while toe-in gives better high-speed stability.
Active camber control is more revolutionary. Under cornering loads, a car leans over and the suspension compresses, which alters the relationship between the tire tread and the road surface. On something as low and firmly suspended as a Lamborghini supercar, the effect is much slighter than it would be on a 1970s sedan, but it is still significant, as it creates uneven pressure distribution on the tire’s contact patch, which reduces grip. Many performance cars are set up with negative camber (the tire leaned in on its inside edge) to compensate for this, but doing so reduces straight-line traction and increases tire wear.
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two rotating flanges within are what alter the relative angle between the two sides, one controlling camber and the other toe. These are gear-driven by 48-volt electric motors.
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The Active Wheel Carrier can deliver up to 6.6 degrees of toe adjustment in either direction and between 2.5 degrees of positive and 5.5 degrees of negative camber. Both planes can be adjusted at the same time, and the electric motors can do this at up to 60 degrees a second. So even the most extreme change possible—from full toe-in to full toe-out—could be accomplished in under a quarter of a second, although most changes will be much smaller adjustments.
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Starting with the system switched off, and the Evo’s rear suspension in its default position, reveals both understeer on cold tires when driven aggressively plus a rapid transition to oversteer when the rear grip is exceeded. With the Active Wheel Carrier switched on, the Huracán immediately feels more grippy and reactive, keener to change direction—much of which is due to the rear-steering effect of toe adjustment—but also much more stable when being pushed to the edge of adhesion.
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On the handling track, our fastest lap with AWC on was 4.8 seconds faster than with the system off, and while that effect is reduced for more experienced drivers on more familiar tracks, it’s still significant. Even a Lambo pro driver is reportedly 2.8 seconds quicker at Nardò with AWC. That’s on par with the gain by switching from sport tires to street-legal semi-slicks.
The technology would also enable other changes: wider front tires relative to the rears, slightly softer springs to allow more roll (active camber being able to adjust to this), and the intriguing possibly of running different tire compounds front and rear to make maximum benefit from the improved grip. Motors powering the units would also likely be upgraded to work on 400 volts, supplied directly from the plug-in-hybrid battery pack.
While AWC is officially only an experiment at this stage, it seems overwhelmingly likely to play a part in Lamborghini’s future—most likely the Huracán replacement that will debut next year.
Source: Lamborghini Tests Active Camber and Toe Control for Better Handling
Robin Edgar
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