McLaren's Approach to Traction: A Deeper Dive into Differential Technology

In the realm of high-performance vehicles, McLaren stands out as a beacon of innovation, particularly in their approach to managing traction without the use of a Limited Slip Differential (LSD). This has sparked a significant debate in automotive circles: If McLaren can achieve exceptional performance without an LSD, how essential is this component?

McLaren's official stance attributes their success to a brake-based torque vectoring system, which offers a lightweight alternative to traditional LSDs. This system leverages existing sensors and brakes, thus avoiding additional weight. However, to fully appreciate McLaren's methodology, it's crucial to understand the mechanics of an open differential, as detailed in our previous blog post here.

An open differential, which allows wheels to turn independently, always maintains a 50/50 torque split. This split is limited by the wheel with the least grip. For instance, if one wheel has 30% less grip, the other wheel can only exert an equivalent amount of torque. When torque exceeds the grip of one wheel, it results in wheel spin.

McLaren's strategy, therefore, focuses on maintaining even grip levels and minimizing weight transfer during cornering. Their Proactive Chassis Control (PCC) plays a pivotal role in this. By eliminating anti-roll bars and employing hydraulically and electronically controlled dampers, with diagonally opposite wheels linked, PCC helps keep the car stable and flat during cornering, ensuring consistent wheel contact.

Additionally, McLaren's sophisticated aerodynamics contribute significantly. By generating extra downforce, they enhance grip and maintain stability in corners. These two factors combined strive to keep grip levels balanced, even during aggressive maneuvers.

However, if these systems were flawless, a brake-based torque vectoring system wouldn't be necessary. This system kicks in when a rear wheel reaches its grip limit, applying braking force to the slipping wheel. This not only creates a pseudo grip level but also aids in rotating the car around the inside wheel. Advanced electronics and sensors continuously calculate the optimal braking pressure.

While McLaren's solution is ingenious, it's not without its drawbacks. Brake-based systems can reduce performance efficiency, as braking a wheel diverts torque that could be used for propulsion, leading to power loss, increased brake wear, and a slight response delay.

Our consultancy has observed that the argument for the extra weight of an LSD doesn't hold much water. An Electronic Mechanical LSD would add a nominal amount of weight (around 20kg), but the performance benefits are substantial. In scenarios where weight is a primary concern, a helical LSD (like Torsen, Quaife, or Wavetrac) could be a more suitable choice, offering minimal weight increase and enhanced torque transfer capabilities.

McLaren's recent model, the Artura subtly acknowledge the potential for improvement in their system. The aftermarket community's widespread adoption of LSD options for McLaren models also suggests a demand for enhanced performance beyond what McLaren's original system offers.

So, why the initial reluctance from McLaren to use LSDs, and why the shift now? It's plausible that McLaren deemed their system with an open differential sufficient for most drivers, prioritizing safety and adequate performance. However, as performance thresholds were pushed, the limitations of electronic systems became apparent, leading to the inclusion of LSDs in newer models for their additional handling benefits.

In conclusion, while McLaren's approach without LSDs is commendable for its sophistication and innovation, it's not a one-size-fits-all solution. Most vehicles lack the advanced electronics and aerodynamics of a McLaren, making a well-tuned LSD a valuable upgrade for enhanced traction and performance. Remember, automotive technology is ever-evolving, and what works for a supercar manufacturer like McLaren may not be the optimal solution for every vehicle.