The focus st wheel size is a critical specification that directly influences the handling, aesthetics, and compatibility of your vehicle. Choosing the correct diameter, width, and offset ensures optimal performance while maintaining the visual integrity of the setup. This guide breaks down the technical nuances to help you make an informed decision.
Understanding Wheel Dimensions
When discussing focus st wheel size, it is essential to look beyond the diameter. The width of the wheel, measured in inches, determines the tire contact patch. A wider wheel allows for a larger tire, which can improve grip during aggressive cornering. However, going too wide can cause the tire to rub against the suspension or fender, especially during full lock or when the vehicle is lowered.
Diameter and Backspacing
The diameter of the wheel, usually ranging from 17 to 19 inches for the Focus ST, affects the overall ride height and the speedometer reading. Larger diameters often accommodate larger brake calipers, which is beneficial for stopping power. Backspacing, or the distance from the mounting surface to the back of the wheel, dictates how far the wheel sits inward. Too little backspacing can push the wheel into the fender, while too much can strain the wheel bearings.
Offset and Its Impact
Offset is measured in millimeters and determines the mounting location of the wheel relative to the hub. A low offset (e.g., -10mm) pushes the wheel outward, giving a more aggressive stance, while a high offset (e.g., 40mm) pulls the wheel inward, creating a more tucked-in appearance. For the Focus ST, maintaining the correct offset is vital to avoid interference with the brakes and suspension components.
Bolt Pattern and Center Bore
The Focus ST typically uses a 5x112 bolt pattern, meaning five lugs are arranged in a circle with a diameter of 112mm. The center bore, the hole in the center of the wheel, must also match the hub closely. While a universal hub-centric ring can compensate for minor mismatches, a precise fit is always recommended to ensure safety and prevent vibration at high speeds.
Performance vs. Aesthetics
Drivers often face a choice between performance and style. A slightly larger wheel with a high-quality tire can improve grip and handling, but it may also add unsprung weight, reducing fuel efficiency and acceleration. Conversely, a smaller wheel with a taller tire might offer a smoother ride but can make the car appear less dynamic. The focus st wheel size should reflect your primary driving environment and style preferences.
Installation and Safety
Aftermarket wheels require careful installation. Using a torque wrench to tighten the lug nuts to the manufacturer's specification is non-negotiable. Over-tightening can strip the threads, while under-tightening can cause the wheel to detach. Furthermore, recalibrating the tire pressure monitoring system (TPMS) and, if necessary, the anti-lock braking system (ABS) is crucial after fitting new wheels.
Compatibility and Modifications
Not all wheels that fit a generic Ford Focus will perfectly suit the ST model due to specific brake clearance requirements. The ST's larger Brembo brakes require wheels with sufficient space between the spokes. If you plan to lower the vehicle, you will need to verify that the wheels do not scrape the suspension during compression. Consulting a fitment guide or a professional installer can save you from costly mistakes.
Conclusion
Selecting the right focus st wheel size involves balancing technical specifications with personal taste. By understanding the relationship between diameter, width, offset, and backspacing, you ensure that your vehicle performs safely and looks the part. Prioritize quality materials and proper installation to get the most out of your upgrade.
