Mclaren 675LT

The history of the McLaren 675LT transcends the launch of a simple sports car; it represents a crucial moment in McLaren Automotive's engineering philosophy. Launched at the 2015 Geneva Motor Show, the 675LT marked the rebirth of the "Longtail" designation, a revered nomenclature that had remained dormant for almost two decades. This report meticulously dissects the genesis, mechanical engineering, advanced aerodynamics, and market impact of this model which, according to experts, redefined the segment of track-focused supercars.

Historical Heritage: The 1997 F1 GTR Longtail

To understand the depth of the 675LT project, it is imperative to revisit its roots. The term "Longtail" originated during the 1997 racing season, when McLaren was forced to evolve its legendary F1 GTR to compete against new dedicated prototypes, such as the Porsche 911 GT1 and the Mercedes CLK GTR. The result was the F1 GTR "Longtail", a car lengthened at the front and rear to maximize downforce and reduce aerodynamic drag.

That 1997 car wasn't just a faster version; it was a complete re-engineering focused on aerodynamic efficiency and an obsessive reduction of weight. When McLaren decided to resurrect this name for the 675LT, the expectation created was not just marketing, but a technical promise: the car would need to be significantly lighter, faster, and more engaging than the model it was based on, the 650S.

Positioning in the "Super Series"

The 675LT was positioned at the top of McLaren's "Super Series", the brand's mid-range, above the 650S and below the P1 hypercar. However, the crucial distinction of the 675LT was its shift in focus. While the 650S was designed to be an everyday usable supercar with great comfort, the 675LT was developed with a singular focus: driver interaction and circuit performance. Production was strictly limited to ensure exclusivity, with only 500 units of the Coupe and 500 units of the Spider initially planned, all sold out quickly, validating the demand for a more visceral machine.

The central pillar of the 675LT's development was weight reduction. McLaren set an ambitious goal of shedding 100 kg compared to the 650S, a Herculean task considering that the 650S already utilized a carbon fiber chassis and was light by class standards.

The MonoCell Monocoque

The foundation of the vehicle is the famous carbon fiber MonoCell structure, which weighs only 75 kg. This central "tub" offers exceptional torsional rigidity, which allowed engineers to remove weight from other areas without compromising structural integrity or safety. The inherent stiffness of the carbon is such that, even in the convertible version (Spider), no heavy additional structural reinforcements were necessary, a significant technical differentiator compared to aluminum or steel competitors.

Carbon Fiber Diet and Exotic Materials

To achieve the target of 1,230 kg (dry weight of the Coupe), the engineering team examined every component of the vehicle:

This meticulous approach resulted in a car with a power-to-weight ratio of 549 PS per tonne, a figure that places the 675LT into hypercar territory.

Although visually similar to the 650S engine, the 675LT's power unit underwent modifications so extensive that it received a new identification code: M838TL. McLaren claims that about 50% of the engine components are new or redesigned specifically for this model.

Detailed Technical Specifications

The engine is a 3.8-liter (3,799 cc) twin-turbo V8 with a flat-plane crankshaft, a characteristic that allows the engine to rev more freely and reach higher RPMs.

• Maximum Power: 675 PS (666 bhp / 496 kW) at 7,100 rpm.
• Maximum Torque: 700 Nm (516 lb-ft) available between 5,500 and 6,500 rpm.
• Rev Limiter: 8,500 rpm.

Internal Components and Response

The main criticism of modern turbo engines is the delay in response (turbo lag). To combat this in the 675LT, the engineers implemented low-inertia internal components:

• Lightweight Connecting Rods: New custom connecting rods reduce the reciprocating mass within the block, allowing the engine to change revs more quickly.
• Camshafts: New cam profiles were designed specifically to optimize airflow at high revs and work in harmony with the new turbos.
• Turbochargers: The turbo units are exclusive to the 675LT. They utilize compressors machined from solid billets for greater aerodynamic efficiency of the blades. Crucially, the wastegates are electronically controlled, rather than pneumatically. This allows for much finer control of boost pressure, smoothing torque delivery and improving immediate throttle response.
• Fuel Pump: A new high-flow fuel pump ensures that the air-fuel mixture remains optimal even under prolonged maximum load on the track.

SSG Transmission and "Ignition Cut"

The 7-speed dual-clutch transmission (SSG - Seamless Shift Gearbox) manufactured by Graziano was recalibrated to offer shifts twice as fast as in the 650S.

In "Track" mode, McLaren introduced a technology called "Ignition Cut". During upshifts, the system momentarily cuts the spark from the spark plugs, interrupting engine torque for a fraction of a second. This allows the gearbox to engage the next gear instantly and creates an explosive "crack" sound in the exhaust, as unburned fuel is ignited in the hot exhaust system. This not only improves performance but adds a visceral auditory theater to the driving experience.

The 675LT's aerodynamics are not just aimed at reducing drag to reach top speeds in a straight line, but rather at generating downforce to increase cornering speed. The aerodynamic package generates 40% more downforce than the 650S, transforming the vehicle's stability at high speeds.

The Active Longtail Airbrake

The most distinct visual characteristic is the "Longtail" Airbrake at the rear. This active wing is 50% larger than the one on the 650S, extending across the entire width of the rear. Despite the increased size, it is lighter due to its carbon fiber construction.

The operation of the Airbrake is complex and adapts to three main scenarios:

• Braking Mode (Airbrake): Under heavy braking, the wing rises to an acute angle, acting as an air brake (similar to a parachute) and shifting the aerodynamic center of pressure rearwards, which stabilizes the rear axle.
• Downforce Mode: In high-speed corners or crests, the wing adjusts its angle to press the rear against the tarmac.
• DRS Mode (Drag Reduction): Under full acceleration in a straight line, the wing aligns horizontally to minimize air resistance.

Splitter and Diffuser

At the front, a prominent carbon fiber splitter channels air underneath the car and to the sides. Vertical plates at the ends of the front bumper (end-plates) generate vortices that clean up the turbulent airflow generated by the spinning front wheels.

At the rear, an aggressive diffuser works in conjunction with the car's flat underbody to accelerate the air passing underneath the vehicle, creating a low-pressure zone that "sucks" the car against the ground.

Dimensions and Physical Changes

Despite the "Longtail" name, the car's physical growth is subtle in terms of overall length, but significant in terms of width and stance.

• Length: The 675LT is slightly longer due to the new bumpers and projected aerodynamics.
• Width: The bodywork is wider at the rear to accommodate the new air intakes and the widened track.

The suspension of the 675LT represents a significant departure from the 650S setup, moving closer to the technology used in the P1 hypercar.

P1-Derived Suspension

The 675LT utilizes the ProActive Chassis Control suspension system, which eliminates traditional mechanical anti-roll bars in favor of an interconnected hydraulic system. However, the hardware has been radically altered:

• Geometry: The front of the car is lower, creating a more aggressive "rake" angle that increases the aerodynamic efficiency of the front diffuser.
• Track: The front track was widened by 20 mm, increasing lateral stability and front axle grip.
• Stiffness: The springs were drastically stiffened: 27% stiffer at the front and 63% stiffer at the rear. This results in much tighter body control, eliminating body roll in corners and dive under braking.
• Lightweight Components: The suspension arms and uprights are derived directly from the P1, contributing to the reduction of unsprung weight and improving the suspension's response to track imperfections.

Steering and Control

McLaren retained hydraulic assistance for the steering, instead of adopting the electric assistance common in the industry. The 675LT's steering rack has a faster ratio than the 650S, making the front of the car incredibly incisive. The retention of hydraulic assistance is widely praised for providing superior tactile "feedback", allowing the driver to feel the texture of the asphalt and the level of grip available from the front tires.

Tires and Brakes

The car came from the factory with Pirelli P-Zero Trofeo R tires, street-legal semi-slick compounds developed specifically to maximize dry track grip. The braking system uses massive carbon ceramic solid discs (CCM) (394 mm at the front, 380 mm at the rear), bitten by six-piston calipers at the front and four at the rear, ensuring immense stopping power and resistance to thermal fade.

The 675LT's lifecycle saw the launch of two main body styles and two ultra-limited special editions.

McLaren 675LT Coupe (2015)

The original version presented in Geneva.

• Production: Strictly limited to 500 units.
• Status: Sold out quickly after the announcement.
• Key Features: It is the lightest and stiffest version, ideal for track purists. The dry weight of 1,230 kg is the benchmark of the range.

McLaren 675LT Spider (2016)

Launched a year later, in response to overwhelming customer demand.

• Production: Also limited to 500 units. Sold out in just two weeks.
• Roof Engineering: Features a three-piece retractable hardtop that can be operated at speeds up to 30 km/h (19 mph).
• Weight Difference: Weighs only 40 kg more than the Coupe (total 1,270 kg dry). This minimal weight penalty is remarkable for a convertible and is due to the absence of heavy structural reinforcements in the carbon chassis.
• Performance:
• 0-100 km/h: 2.9 seconds (equal to the Coupe).
• 0-200 km/h: 8.1 seconds (only 0.2s slower than the Coupe due to aerodynamics and marginal weight).
• Top Speed: 326 km/h (Coupe reaches 330 km/h).

MSO Carbon Series (2016)

Based on the Spider, this edition was created by the McLaren Special Operations (MSO) division.

• Production: Limited to 25 units worldwide.
• Differential: Features 40% more carbon fiber than the standard LT. The entire bodywork is clad in gloss visual carbon fiber, including the retractable roof, the tonneau cover, and the A-pillars, which were painted on the standard model.
• Exclusivity: It was offered only to customers who already owned a 675LT or a P1, and all units were sold before the public announcement.

MSO HS (High Sport) / 688 HS (2016-2017)

The final and most extreme evolution of the platform.

• Name: Officially "MSO HS", but known as "688 HS" due to its power.
• Production: 25 units.
• Technical Improvements:
• Power: Increased to 688 PS (679 bhp).
• Aerodynamics: Includes a massive fixed rear wing (GT3 style) that works in conjunction with the active airbrake, plus functional louvres on the front fenders to extract high-pressure air from the wheel arches.
• Roof Scoop: Most units feature a functional roof scoop (snorkel) that feeds the engine and amplifies the induction sound in the cabin.
• Weight: 40 kg lighter than the standard 675LT.
• Torque: 700 Nm, available over a wider rev band (3,000 to 7,000 rpm).

To understand the magnitude of the 675LT's engineering, we present a direct comparative table with the base 650S model:

Engineering Insight: The simple reading of the 0-100 km/h numbers (3.0s vs 2.9s) hides the true difference. The limitation at low speeds is tire traction. The 675LT's true advantage reveals itself above 100 km/h, where superior aerodynamics and power-to-weight ratio allow it to quickly pull away from the 650S.

The interior of the 675LT is an exercise in functional minimalism.

Focused Cockpit

• Seats: Carbon fiber bucket seats based on the P1 are standard. They offer extreme lateral support, essential for the G-forces the car generates in corners.
• Trim: The extensive use of Alcantara instead of leather saves weight and reduces reflections on the windshield. Air conditioning was removed from the standard configuration to save 11 kg, but could be added back at no cost (an option chosen by most buyers).
• Noise, Vibration, and Harshness (NVH): McLaren purposely reduced acoustic insulation. The sound of stones hitting the carbon wheel arches, the whine of the transmission, and the roar of the titanium exhaust enter the cabin unfiltered. Furthermore, the engine mounts are 300% stiffer, transmitting the vibrations of the V8 directly to the carbon chassis and the driver's back, increasing the sense of mechanical connection.

Active Dynamics Panel (ADP)

On the center console, the driver finds the ADP, which controls the car's character:

• Powertrain Modes: Normal, Sport, and Track (activates "Ignition Cut" and opens exhaust valves).
• Handling Modes: Normal, Sport, and Track (stiffens the suspension and relaxes the ESC stability control).
• McLaren Track Telemetry (MTT): An integrated system with cameras and GPS allows recording laps on circuits and analyzing telemetry data on the central screen.

McLaren offered a vibrant and historic color palette for the launch of the 675LT. The colors helped define the aggressive personality of the car.

Launch and Popular Colors

• Chicane Grey: A solid, technical, and menacing grey, it became the model's signature color, frequently combined with an orange interior.
• Napier Green: A bright, acidic green.
• McLaren Orange: The brand's historical orange.
• Delta Red: A deep red.
• Silica White: Pearlescent white.

In addition to these, the MSO division allowed painting the car in practically any desired color for an extra cost.

Being a high-performance supercar, maintenance is rigorous, but the 675LT is considered mechanically robust, benefiting from the maturity of the platform that started with the 12C.

Points of Attention

• Suspension Accumulators: The suspension's hydraulic system has accumulators that can lose pressure over time, resulting in an overly harsh and bouncy ride. Replacement is a known maintenance item.
• Coolant Leaks: Hose clamps can loosen due to vibration, causing small coolant leaks.
• Windshields: Due to reduced thickness (to save weight), the windshield is more susceptible to cracking from stone impacts.
• Brakes: Carbon ceramic discs last a long time in street use, but intensive track use may require expensive replacements.

The McLaren 675LT ended its production in 2017, but its impact endures. It established the formula for all future "LT" models from the brand (like the 600LT and the 765LT): reduced weight, active aerodynamics, and total focus on driver involvement.

For many collectors and automotive journalists, the 675LT remains McLaren's modern "sweet spot". It combines the compact size and communicative hydraulic steering of the older generation with performance that even today, years after its launch, is capable of humbling much newer supercars. With only 1,000 main units produced (500 Coupe + 500 Spider), it secured its place in history as one of the great analog-digitals of its era.

The combination of exclusivity, the purity of hydraulic steering (a technology that is disappearing), and the brutality of the M838TL engine make the 675LT not just a chapter in McLaren's history, but an entire volume dedicated to the pursuit of dynamic perfection.