Driving dynamics: steering, brakes and transmission

Driving dynamics: steering, brakes and transmission  - Overview - Volvo XC70

All XC70 models get Volvo's innovative AWD (All-Wheel Drive) transmission as standard. This advanced system, which automatically apportions torque front-to-rear depending on need, improves the XC70's handling and stability on the road. But it also improves traction and handling when the road runs out.

The Volvo XC70 has sharp and agile handling irrespective of conditions. The strong, large disc brakes are supplemented by a host of advanced electronic features to ensure that the XC70 always stops in the shortest possible distance, whether you're driving on the motorway or in the mud. A number of new primary safety technologies are available on the XC70, including Volvo's innovative Collision Warning with Auto Brake, which monitors the distance to the car in front and then optimises braking strength to help you avoid accidents.

All-Wheel Drive standard

The Volvo XC70 is a rugged car aimed at people who really do use their cars off-road. 'It's an all-road car, good on the road and good off the road,' says Tomas Ahlborg. 'Far more than most SUVs, customers genuinely use their XC70s to go into the wild. But as we say at Volvo, you use an XC70 to drive to nature not to drive over nature.'

The Volvo XC70's AWD system improves handling and road holding by apportioning torque to all four wheels. The computer-controlled Haldex Coupling automatically sends torque to the wheels with most grip, ensuring maximum possible traction and primary safety. The front-to-rear torque split changes constantly, as the sophisticated electronics control a hydraulic clutch that determines the most effective distribution of torque.

Sensors monitor the road (or off-road) surface and the positions of the steering, brake and accelerator. In normal conditions on a dry tarmac road, almost all the power is distributed to the front wheels. However, as soon as slippage occurs, such as in muddy off-road conditions, torque is diverted to the rear wheels to boost grip.

This unique system also features Volvo-patented Instant Traction, which detects loose or slippery surfaces and switches drive from front to rear (or vice versa) to help with standing starts.

AWD improves traction on all slippery surfaces, such as gravel, mud, snow, sand or ice, and it allows the car to go anywhere, since all four wheels provide grip. But it also improves the handling balance of the car on the road. Unlike many mechanical systems fitted to SUVs, Volvo's electronic AWD system is light - reducing unsprung weight and improving both fuel consumption and on-road handling balance.

Six-speed automatic or manual gearbox

The D5 gets a choice of six-speed manual or six-speed Geartronic automatic transmission.

The modern Geartronic transmission can be used either as a full automatic or as a clutchless manual. In automatic mode, gear changes are so smooth as to be almost imperceptible.

The six-speed manual improves both performance and fuel economy, and is a smooth-shifting clutch-and-stick shift aimed at those who prefer changing gear themselves.

Highly advanced interactive braking system

The Volvo XC70 has ABS anti-lock brakes to stop skids and aquaplaning on- and off-road, and big disc brakes - ventilated at the front - all round. The brakes are 316mm in diameter at the front and 302mm at the rear. The new model also has a suite of advanced, interconnected braking features to deliver the best possible stopping performance. They include:

HBA (Hydraulic Brake Assist). This is an update of Volvo's previous EBD (Electronic Brakeforce Distribution) and EBA (Emergency Brake Assist). This new-generation system, first shown on the latest S80, helps the driver to stop in the shortest possible distance in emergency situations. Unlike the previous system, which only used vacuum assistance to boost braking strength, HBA reinforces brake pressure hydraulically. In an emergency, when the driver does not press the pedal sufficiently firmly or quickly, HBA ensures that maximum braking pressure is applied, always giving the driver the greatest chance to reduce the likelihood, or seriousness, of an accident.
OHB (Optimised Hydraulic Brakes). In heavy braking, vacuum pressure in the brake servo can become low, reducing braking effort. OHB compensates by using hydraulic pressure to boost braking effort.
RAB (Ready Alert Brakes). If the accelerator is released suddenly or the adaptive cruise control registers an obstacle in front of the car, RAB is deployed. The brake pads are instantly positioned very close to the discs, reducing braking response time and braking distance.
FBS (Fading Brake Support). In long, hard braking, such as on a lengthy, mountainous descent, there is a risk of brake fade. FBS uses the hydraulics to gradually build brake pressure, maintaining pedal feel.

Collision Warning with Auto Brake

This clever new technology, first shown on the latest Volvo S80 and now also available on the Volvo XC70 and V70, reduces the risk of rear-end accidents; where an impact is inevitable, it should reduce its severity.

A radar sensor, fitted behind the grille, continually monitors the area in front of the vehicle. If the sensor detects that the car in front has braked suddenly, that you are too close to the vehicle in front, or that there is an obstacle in your path, a red warning lamp flashes on the windscreen and a warning buzzer sounds. In many situations, this will be sufficient to alert the driver and the danger will pass. However, if the risk of collision increases, the brake support system is activated. The pads move very close to the brake discs and the hydraulic brake pressure is increased. Thus the brakes are fully prepared for a panic stop. Even if weak pressure is applied to the brake pedal, maximum brake pressure will be automatically used to cut stopping distance. The driver's reactions remain crucial, however - the car will never apply the brakes automatically.

To warn traffic behind, the brake lights will start to flash when the brakes have been applied in this way. Once the speed drops below 30km/h (19mph), the hazard warning flashers are also automatically activated.

The sensitivity of the collision warning system can be adjusted via the car's settings menu. There are three different positions that can be set according to driving style or road conditions.

Adjustable, speed-dependent power steering

All Volvo XC70s get sharp, power-assisted rack and pinion steering as standard. On the SE Sport, speed-dependent power steering is standard. This provides extra power assistance at low speeds, for example to make parking easier. The power assistance gradually declines as road speed increases, disappearing entirely at high cruising speeds. To give all drivers their own optimum road feel, the level of steering servo assistance can now be adjusted via the car's set-up system. Power steering assistance can be set at one of three levels, depending on personal taste.

Power Parking Brake

This smart parking brake is released automatically once the accelerator is pressed (and the driver's seatbelt is fastened), making hill starts easier, especially for cars fitted with manual gearboxes. The parking brake is engaged by pushing a lever to the left of the steering wheel and can be manually disengaged by pulling the same lever. The parking brake is automatically engaged once the key is removed from the ignition or, for models with keyless drive, when the driver's door is opened.

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