四輪駆動アイルランド
67. 四輪駆動
四輪駆動(4WDまたは4x4)は、車両の4輪すべてへ駆動力を伝えられる駆動方式です。雪、泥、砂利、砂、不整地などで追加のトラクションを得られます。
常時作動する方式と、必要時に自動または手動で作動させる方式があります。滑りやすい路面や悪路での走破性を高めますが、適切なタイヤ、安全な速度、慎重な制動・操舵が不要になるわけではありません。
What is four-wheel drive?
Four-wheel drive is a drivetrain system that can send power to all four wheels of a vehicle rather than only the front or rear wheels.
What does 4x4 mean?
4x4 normally indicates a vehicle with four wheels of which all four can be driven by the powertrain.
Is four-wheel drive the same as all-wheel drive?
The terms 4WD and AWD are sometimes used interchangeably, but manufacturers often use them for different types of system. Traditional 4WD systems commonly provide selectable driving modes, while AWD systems often distribute power automatically.
Does four-wheel drive improve traction?
Yes. Sending power to more wheels can improve traction when accelerating on snow, mud, gravel, sand or other low-grip surfaces.
Does four-wheel drive shorten braking distance?
Not automatically. Braking performance depends primarily on the tyres, road surface, speed, braking system and vehicle condition. Four-wheel drive should not encourage a driver to travel faster on slippery roads.
Does a four-wheel-drive vehicle still need suitable tyres?
Yes. The tyres provide the contact between the vehicle and road. Four-wheel drive cannot compensate for tyres that are unsuitable, excessively worn or incorrectly inflated.
Can four-wheel drive help in snow?
Yes. It can improve the ability to move away and climb on snow-covered roads, but safe braking and cornering still depend heavily on tyre grip and appropriate speed.
Can a four-wheel-drive vehicle drive off-road?
Some 4x4 vehicles are designed for off-road use, but four-wheel drive alone does not make every vehicle suitable for difficult terrain. Ground clearance, tyres, suspension and the drivetrain design are also important.
Can you use four-wheel drive on dry roads?
This depends on the type of drivetrain. Permanent or automatic systems are designed for normal road use, while some selectable 4WD systems should only be engaged under particular conditions. Follow the manufacturer's instructions.
Does four-wheel drive increase towing capacity?
It can improve traction when towing, but the legally and technically permitted trailer mass is determined by the vehicle's approved towing limits and local regulations, not simply by the presence of four-wheel drive.

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