What is the drag coefficient of the Ford Sierra?
The drag coefficient is typically about 0.32–0.34 for standard Ford Sierra hatchbacks, with slight variation by model and year.
The exact value depends on the Sierra variant, year, and aero details such as spoilers, roof rails, wheel choices, and underbody coverage. The following article explains the common figures, what influences them, and how they relate to real-world performance and efficiency.
What the drag coefficient means and why it matters
The drag coefficient (Cd) is a dimensionless number that quantifies how aerodynamic a body is. For cars, a lower Cd generally means less air resistance at speed, which can improve fuel efficiency and high-speed performance. The Ford Sierra, introduced in the early 1980s, was designed with aerodynamics in mind, but its boxier silhouette compared with modern cars kept Cd in a mid-0.3 range rather than a low-0.2 figure seen on sleeker designs.
Typical values across Sierra configurations
Below are commonly cited approximate Cd ranges for representative Sierra configurations. Values can vary by year, trim, and testing method, so treat these as guidance rather than exact specifications.
- Standard hatchback (Mk1/Mk2 era): Cd ≈ 0.32–0.34
- Estate/variant with extended tail: Cd ≈ 0.34–0.36
- Four-wheel-drive versions: Cd ≈ 0.36–0.40
- RS/Cosworth and other performance variants: Cd ≈ 0.34–0.36
Note that the above ranges reflect typical reports from manufacturers, car magazines, and historic specifications. Actual numbers can differ by market, wheel/tyre size, optional aero bits, and whether testing included accessories such as roof racks or spoilers.
Factors that influence the Sierra’s drag coefficient
Several design and equipment factors can shift the Cd value for any Sierra example.
- Body style (hatchback vs estate vs saloon): different rear profiles change wake and flow separation
- Aero add-ons (spoilers, front air dams, side skirts): reduce turbulence and shear
- Roof-mounted items (carrying racks, rails): increase drag if present
- Wheel size and tires: affect under-body airflow and tire turbulence
- Underbody treatment and panels: smoother undertray and panels lower drag
- Testing conditions and measurement standards: Cd can vary with speed and test setup
In practice, the Sierra’s Cd is a balance between perception of aerodynamics and the era’s design norms. Real-world fuel economy and performance depend on more than Cd alone, including gearbox, engine power, weight, and rolling resistance.
Why Cd values matter for enthusiasts and historians
Understanding the Sierra’s Cd helps explain how a car built in a boxy era could still offer respectable highway efficiency for its time. While modern wind-tunnel optimized designs achieve Cd values well below 0.30, the Sierra represents a transitional period where styling and practicality often trump achieving the absolute lowest drag.
Summary
For the Ford Sierra, the drag coefficient typically sits in the 0.32–0.34 range for standard hatchbacks, with modest increases for estate and 4x4 variants. Performance-oriented versions may hover in a similar band, while specific aero packages and testing conditions can nudge numbers up or down by a few hundredths. The exact Cd depends on the model year, body style, and optional aero components. Overall, Cd provides a useful lens to compare aerodynamics across Sierra variants and to understand how design choices affected efficiency and performance in the era.
What car has the highest drag coefficient?
- McLaren Speedtail (2020-present) Drag coefficient: 0.278 Cd.
- Vauxhall Calibra (1989-97) Drag coefficient: 0.26Cd.
- Tesla Model 3 (2017-present)
- Porsche Taycan (2019-present)
- Mercedes A-Class Saloon (2018-present)
- BMW 5 Series Efficient Dynamics (2011-13)
- Tatra T77A (1935-38)
- Tesla Model S (2012-present)
Is 0.28 drag coefficient good?
Yes, a drag coefficient of 0.280.280.28 is considered good, as it is below the average for modern cars, which typically ranges between 0.250.250.25 and 0.300.300.30. It indicates a streamlined design that improves fuel economy and performance, and is a respectable number, especially for vehicles that aren't designed for extreme aerodynamic efficiency.
What a 0.280.280.28 drag coefficient means
- Efficiency: A lower drag coefficient means less air resistance, which requires less power to maintain speed, leading to better fuel economy and longer range for electric vehicles.
- Performance: A lower drag coefficient contributes to a higher top speed and better stability at high speeds.
- Comparison: It is a strong value, shared by models like the Ford Mustang Mach-E and certain versions of the Volkswagen Golf and Toyota GT86.
- Context: For larger, less aerodynamic vehicles like SUVs, a 0.280.280.28 is an impressive achievement, as their shape naturally creates more drag.
- Aerodynamic limitations: While 0.280.280.28 is good, more extreme examples exist, such as the Tesla Model S Plaid (0.2080.2080.208) and the Koenigsegg Absolut (<0.28), which are designed for even lower drag.
What is the drag coefficient of a truck?
1. The coefficient of drag of a heavy-commercial vehicle is around 0.8 [2]. The drag force is increased due to the large frontal areas and bluff-body shape [3]. When travelling on the highway with 100 km/h speed, a 40-tonne truck is estimated to consume around 40 L of fuel.
What is the drag coefficient of the Chevy Silverado 1500?
To help the All-New Silverado achieve a . 38 drag coefficient and a 7.5% improvement in aerodynamics, Chevrolet engineers spent over 500 hours in the wind tunnel, testing airflow around the vehicle. A longer wheelbase and wide, muscular stance provide a powerful base.
