XF Suspension, Brakes and Wheels

Suspension

The XF’s class-leading torsional rigidity has significant benefits for refinement and provides the perfect platform for a suspension system that is a further development of the Jaguar XK sports car, and delivers a ride/handling balance and steering characteristics absolutely in line with the XF’s sporting looks. Unequal length wishbone front suspension with weight-saving aluminium components, and multi-link rear suspension are both subframe mounted for maximum control, including excellent straight-line stability and strong anti-dive characteristics under heavy braking, with minimum road noise and vibration.

The only suspension variations on the XF are between the V6 petrol, V6 diesel and V8 naturally aspirated models, which all use finely tuned passive suspension, and the SV8, which for all markets uses Jaguar’s Computer Adaptive Technology Suspension (CATS TM). The latest CATS TM is a sophisticated system shared with the new Jaguar XK sports grand tourer. It uses electronically controlled, two-stage, adaptive dampers whose characteristics are automatically adjusted within milliseconds in response to road conditions and driving inputs, for the optimum balance between comfort and control.

Brakes

The XF uses large 326mm x 20mm vented front discs on all naturally aspirated models and 355mm x 32mm vented front discs on the SV8 model for powerful, balanced braking performance. The rear discs on all versions measure 326mm x 20mm.

An extremely stiff pedal box contributes to a particularly solid pedal feel, and the brake assistance is tuned to give a very progressive feel, while softening the initial response.

The XF uses Jaguar’s Electric Parking Brake, with a small and neat, chromed release in the centre console. As the XF’s braking system communicates electronically with the shift-by-wire technology of the JaguarDrive Selector TM function, so the Parking Brake is released automatically as Drive is selected – although the Parking Brake can also be engaged and disengaged manually if appropriate.

Steering

Variable ratio power-assisted steering is standard on every version of XF, for reduced parking effort at low speeds and greater precision and feedback at higher speeds - and especially for positive weight to the on-centre feel, which is part of the new dynamic flavour. Steering effort at manoeuvring speeds is also reduced on diesel models.

The new XF adopts an electronic steering column lock – for compatibility with passive entry mode and the Jaguar Smart Key System TM. There is no longer a key barrel on the column, however the electronic lock satisfies Thatcham security legislation for the UK market.

The XF’s steering wheel includes cruise-control, JaguarVoice TM (where fitted) and audio controls - including volume, and radio channel pre-sets. The source button toggles through AM/FM/CD, plus any external device functions. The select buttons allow features such as CD track change, radio channel pre-set selection or iPod® or MP3 track change if such a device is in use.

Wheels and Tyres

Depending on market and model, the XF is available with 17, 18, 19 or 20-inch wheels; the SV8 being the only car in its class to have 20-inch wheels as standard. All are cast in aluminium alloy and every design combines maximum strength with minimum weight. To satisfy Thatcham security stipulations, there are also 20 variations of anti-theft locking nut. All cars for the majority of markets carry the same specification of 18-inch diameter alloy mini-spare.

For major European markets, cars with 17 and 18-inch wheels are fitted with the Jaguar Tyre Repair System as a space and weight-saving alternative to the ‘mini-spare’. This replaces the spare wheel, jack and tool kit, and can effect a temporary repair of any puncture of up to 6mm diameter in the tread area - sealing the hole and re-inflating the tyre to enable the car to be driven to where a permanent repair or replacement can be carried out. When fitted in lieu of a spare wheel, the Jaguar Tyre Repair System liberates an additional 40 litres of stowage space under the boot floor.

Driver Aids

The XF’s main control module governs many key safety functions including Emergency Brake Assist (EBA), Electronic Brakeforce Distribution (EBD), Anti-lock Braking System (ABS), Traction Control through engine and brake intervention, Dynamic Stability Control (DSC), Cornering Brake Control (CBC) and Engine Drag Torque Control. And for the first time, the XF adds Understeer Control Logic, which has been designed to mitigate understeer by intervening through the engine management and braking systems to decelerate the car and help restore grip to the front wheels.

A two-stage DSC system similar to that featured on the new XK is standard. It combines the normal on-off switchable DSC function, which reacts as soon as it detects slip, with Trac DSC, which allows more slip before intervening – better for a more sporting driving experience. It also allows a degree of wheel overspin on deep soft surfaces, which is essential for running with snow chains. The system defaults to normal ‘DSC on’ with each ignition-on sequence.

In Dynamic Mode (SV8 only), pressing and holding the DSC button fully disables the system, allowing an experienced driver to exploit fully the capability of the chassis, where conditions allow. Mode selection is confirmed on the instrument cluster display.

Also new on XFs fitted with Adaptive Cruise Control (ACC) is Electronic Brake Prefill. This senses any rapid throttle lift-off and initiates a small brake hydraulic pressure build-up in anticipation of the brakes being applied, to give better pedal response and slightly shorter stopping distances.

JaguarDrive Control TM offers different modes that interact with the DSC system, engine and gearbox, to change the characteristics of engine mapping, transmission shifts and brake interventions depending on driving conditions and circumstances. On naturally aspirated cars JaguarDrive Control TM has Normal and Winter modes, on the SV8 model there are Normal, Winter and Dynamic modes - the last of these to allow a more purposeful driving style.