2015 Subaru WRX STI: Wheel Specs Guide

by Alex Braham 39 views

Hey Subaru enthusiasts! If you're looking to upgrade or replace the wheels on your 2015 Subaru WRX STI, you've come to the right place. This guide dives deep into the wheel specifications for this iconic car, ensuring you make the best choices for performance, aesthetics, and fitment. Let's get started!

Understanding Wheel Specs

Before we jump into the specifics for the 2015 WRX STI, let's cover some fundamental wheel terminology. Knowing these terms will help you understand the numbers and make informed decisions. Understanding wheel specs is crucial for ensuring proper fitment and performance. So, what are these terms we need to familiarize ourselves with?

  • Diameter: This is the overall size of the wheel, measured from one end to the other through the center. It's usually measured in inches. For example, a 17-inch wheel has a diameter of 17 inches.
  • Width: The width refers to the measurement from one inner edge of the wheel to the other, also in inches. The width of the wheel determines what tire sizes you can safely mount. A wider wheel can typically accommodate a wider tire.
  • Bolt Pattern (PCD): Bolt pattern, also known as Pitch Circle Diameter (PCD), is the diameter of the circle formed by the centers of the wheel's bolt holes. It's specified by the number of bolts and the diameter of this circle. For example, a 5x114.3 bolt pattern indicates five bolts on a circle with a diameter of 114.3mm.
  • Offset: Offset is the distance from the wheel's mounting surface to its centerline, measured in millimeters. A positive offset means the mounting surface is closer to the outside of the wheel, while a negative offset means it's closer to the inside. Offset affects how the wheel sits in the wheel well and can impact steering and suspension geometry.
  • Center Bore: This is the diameter of the center hole in the wheel, which centers the wheel on the vehicle's hub. If the center bore of the wheel is smaller than the hub diameter, the wheel won't fit. If it's larger, you might need hub-centric rings to ensure proper centering and reduce vibration.

Why is each of these important? The diameter dictates the overall look and feel of your car, plus it affects tire options. The width must match the tire you intend to use, and of course, the bolt pattern is absolutely critical; get it wrong, and the wheel simply won't attach. Offset influences both the appearance (how far the wheel sticks out or tucks in) and the handling of your car. Finally, the center bore ensures the wheel is properly aligned, which is vital for safety and smooth driving. Each of these specs plays a crucial role in ensuring that your wheels fit correctly and perform as expected.

Stock Wheel Specs for the 2015 Subaru WRX STI

Okay, let’s dive into the OEM (Original Equipment Manufacturer) wheel specifications for the 2015 Subaru WRX STI. Knowing the stock specs is essential whether you're looking to replace your wheels with the same size or upgrade to something different. Here’s what you need to know:

  • Diameter: 18 inches
  • Width: 8.5 inches
  • Bolt Pattern (PCD): 5x114.3mm
  • Offset: +55mm
  • Center Bore: 56.1mm

So, your factory wheels are 18 inches in diameter and 8.5 inches wide. The bolt pattern is 5x114.3mm, which is a common pattern for many Japanese vehicles. The offset is +55mm, which means the wheel's mounting surface is 55mm towards the outside of the wheel's centerline. The center bore is 56.1mm, ensuring a snug fit on the hub. These stock wheel specs are what Subaru designed the car to use, so sticking close to them is generally a safe bet.

Why are these specifications important? Well, if you're just looking to replace a damaged wheel with an identical one, these are the numbers you need to match. However, if you're considering aftermarket wheels, knowing these specs gives you a baseline to work from. You can then decide if you want to go wider, change the offset for a different stance, or opt for a different diameter. Remember, changing any of these specs can affect your car's handling, ride quality, and even tire wear, so it’s good to be informed. Knowing the OEM wheel specifications provides a solid foundation for any wheel upgrade or replacement project.

Aftermarket Wheel Considerations

Now that we know the stock specs, let’s talk about aftermarket wheels. Upgrading to aftermarket wheels can significantly change the look and performance of your 2015 WRX STI. However, there are several things to consider to ensure you get the right fit and performance. When considering aftermarket wheel considerations, you should keep a few things in mind to ensure optimal results.

  • Size and Fitment: While you can deviate from the stock size, it’s crucial to ensure the new wheels fit without rubbing or causing any mechanical issues. A slightly wider wheel (e.g., 9 or 9.5 inches) can improve handling and tire grip, but make sure the offset is appropriate to avoid fender rubbing.
  • Offset Changes: Adjusting the offset can alter the stance of your car. Lower offsets push the wheels outward, giving a more aggressive look. However, going too far can lead to clearance issues with the fenders and suspension components. A good rule of thumb is to stay within +/- 10mm of the stock offset unless you know exactly what you're doing.
  • Material and Weight: Aftermarket wheels come in various materials, including aluminum alloy, forged aluminum, and even carbon fiber. Lighter wheels can improve acceleration, braking, and handling. Forged wheels are typically stronger and lighter than cast wheels, but they're also more expensive. Selecting the right material and weight is essential for maximizing performance gains.
  • Style and Aesthetics: Of course, the look of the wheels is a major factor. Choose a style that complements the WRX STI’s aggressive lines. Popular options include mesh designs, split spokes, and concave faces. The key is to find wheels that not only look good but also meet your performance requirements. Consider how the wheel finish (e.g., matte black, silver, bronze) will look with your car's paint color.
  • Brake Clearance: If you're planning to upgrade your brakes in the future (or already have), make sure the wheels you choose have enough clearance for the calipers. Some wheels have designs that don't work well with larger brake kits. Double-check the wheel specifications or consult with a wheel specialist to ensure compatibility.

Before purchasing, it's a great idea to test fit the wheels if possible. Many tire shops will allow you to mount a wheel temporarily to check for clearance issues. Also, read online forums and communities dedicated to the WRX STI. You'll find a wealth of information and experiences from other owners who have already gone through the wheel upgrade process. All of this will help ensure that your aftermarket wheel considerations lead to a successful and satisfying upgrade.

Tire Size Considerations

Choosing the right tire size is just as important as selecting the right wheels. The tire size affects everything from ride comfort to handling and speedometer accuracy. The stock tire size for the 2015 WRX STI is 245/40R18. However, depending on your new wheel size, you might want to consider different tire sizes. When thinking about tire size considerations, you have to make sure that they work well with the wheels and your car's capabilities.

  • Maintaining Overall Diameter: When changing tire sizes, it’s important to maintain the overall diameter of the tire to avoid affecting your speedometer readings and the car’s traction control system. You can use online tire size calculators to compare different sizes and see how they affect the overall diameter.
  • Wider Tires for Improved Grip: If you’ve upgraded to wider wheels, you can also consider wider tires for improved grip. For example, a 255/40R18 or 265/35R18 tire can provide more traction, especially during cornering. However, be cautious of potential rubbing issues, especially on the rear fenders.
  • Aspect Ratio: The aspect ratio is the height of the tire sidewall as a percentage of its width. A lower aspect ratio (e.g., 35 vs. 40) means a shorter sidewall, which can improve handling but may also result in a harsher ride. A higher aspect ratio provides more cushioning and a smoother ride but may compromise handling.
  • Load Rating and Speed Rating: Ensure the tires you choose have an appropriate load rating and speed rating for your vehicle. The load rating indicates the maximum weight the tire can carry, while the speed rating indicates the maximum speed the tire is designed to handle. Exceeding these ratings can be dangerous.
  • Tire Brands and Types: Consider the type of driving you do most often. If you're primarily on the street, a good set of performance summer tires or all-season tires will work well. If you track your car, you might want to invest in a set of dedicated track tires. Research different tire brands and read reviews to find the best option for your needs.

Before making a decision, consult with a tire specialist who can provide recommendations based on your driving style and the wheel size you've chosen. Also, check online forums and communities for insights from other WRX STI owners. Paying attention to these tire size considerations will help you choose the right tires to complement your new wheels and enhance your driving experience.

Potential Issues and Solutions

Upgrading your wheels can sometimes lead to unexpected issues. Knowing these potential problems and their solutions can save you a lot of headaches. Addressing potential issues and solutions proactively will help ensure a smooth upgrade process.

  • Rubbing: One of the most common issues is tire rubbing against the fenders, especially when using wider wheels or tires. This can be caused by an incorrect offset or a tire size that’s too large. The solution may involve rolling the fenders (bending the inner lip of the fender), using a slightly narrower tire, or adjusting the offset.
  • Clearance Issues with Suspension Components: In some cases, the new wheels might rub against the suspension components, such as the struts or control arms. This is more likely to occur with wheels that have an incorrect offset or a very wide width. Ensure you have enough clearance between the wheel and all suspension parts.
  • TPMS Compatibility: If your 2015 WRX STI is equipped with a tire pressure monitoring system (TPMS), you’ll need to ensure that the new wheels are compatible with the TPMS sensors. Some aftermarket wheels may require different sensors or adapters. Ensure the sensors are correctly installed and calibrated after the wheel installation.
  • Vibration: Vibration can occur if the wheels are not properly balanced or if the center bore of the wheel doesn't match the hub. Ensure the wheels are professionally balanced and, if necessary, use hub-centric rings to properly center the wheel on the hub. Vibration can also be caused by damaged tires or bent wheels, so inspect your wheels and tires regularly.
  • Steering Feel: Changing the wheel size or offset can alter the steering feel. Some people may find that the steering becomes heavier or less precise. Experiment with different setups to find what works best for you. In some cases, adjusting the alignment can help improve steering feel.

By being aware of these potential issues and their solutions, you can tackle any challenges that arise during the wheel upgrade process. Thorough research and careful planning are key to a successful outcome. Always consult with professionals when needed, and don't hesitate to ask for advice from other WRX STI owners. Taking these potential issues and solutions into account can help you avoid common pitfalls and achieve the desired look and performance for your ride.

Conclusion

Choosing the right wheels for your 2015 Subaru WRX STI can significantly enhance its appearance and performance. By understanding wheel specifications, considering aftermarket options, and paying attention to tire sizes, you can make informed decisions that improve your driving experience. Remember to address potential issues and consult with professionals when needed. With the right set of wheels, your WRX STI will not only look great but also perform at its best. Happy motoring, guys! Have fun and drive safe!