To free wheel or coast in a car refers to a specific driving technique where the driver intentionally disengages the engine from the wheels.
According to driving practice guidelines, freewheeling or coasting is a bad driving practice involving the driver either driving with the clutch depressed or the gear stick in neutral, or both together. This action disengages the wheels from the engine's power and resistance.
How Freewheeling is Done
The technique involves two primary methods:
- Depressing the Clutch: In a manual transmission vehicle, holding the clutch pedal down isolates the engine from the gearbox and wheels.
- Shifting to Neutral: Moving the gear stick to the neutral position (N) achieves the same isolation, regardless of transmission type (manual or automatic).
The Intended Purpose of Coasting
As the reference notes, the primary motivation behind coasting is typically to save fuel. Since the vehicle must be going downhill, it allows the vehicle to travel without consuming extra fuel. By letting gravity propel the car, the engine idles or is disengaged, theoretically using less fuel than if it were powering the vehicle or providing engine braking.
Why Freewheeling is Considered a Bad Driving Practice
Despite the potential for fuel savings, freewheeling is widely regarded as unsafe and a poor driving habit. Here's why:
- Reduced Control: Disengaging the engine significantly reduces the driver's control over the vehicle. Engine braking, the resistance provided by the engine when the accelerator is released in gear, is lost. This forces greater reliance solely on the friction brakes, which can lead to overheating and reduced effectiveness, especially on long descents.
- Impaired Acceleration: If a sudden need to accelerate arises (e.g., to avoid an obstacle), the driver must re-engage the engine (release clutch, select a gear). This takes crucial time and can hinder the ability to react quickly in an emergency.
- Potential Loss of Systems: In some older vehicles, or under certain specific conditions, sustained coasting could potentially affect the performance of power steering or power brakes, as these systems often rely on the engine running normally in gear. Modern cars are less susceptible, but control is still compromised.
- Increased Brake Wear: With engine braking removed, the vehicle's speed must be controlled entirely by the friction brakes, leading to faster wear and potential failure under heavy use.
Summary Table: Freewheeling
| Aspect | Description | Implication |
|---|---|---|
| Action | Clutch depressed OR Gear in neutral OR Both | Disengages engine from wheels |
| Location | Typically done going downhill | Relies on gravity for movement |
| Intended Benefit | Allows travel without consuming extra fuel (per reference) | Potential minor fuel saving |
| Status | Bad driving practice (per reference) | Unsafe due to reduced control |
In conclusion, while a car capable of shifting into neutral or having a clutch can be freewheeled, the term "free wheeling car" describes the action taken by the driver rather than a specific type of vehicle built for this purpose. It is an unsafe technique that compromises vehicle control.
