How to Choose the Right Aftermarket Wheels for Your Car
Upgrading your wheels? Learn how to choose the perfect aftermarket wheels by understanding PCD, offset, width, clearance, and speedometer accuracy in our expert guide
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Upgrading your wheels is one of the best ways to enhance your car’s appearance, handling, and performance. However, picking the right set isn’t just about choosing a design you like. There are multiple factors to consider, such as PCD, offset, width, clearance, and speedometer accuracy.
In this guide, we’ll break down everything you need to know to make sure that your wheels fit properly and and more importantly they are safe for the road/track.
Understanding PCD (Pitch Circle Diameter)
What is PCD?
PCD refers to the diameter of the imaginary circle that passes through the centre of your wheel’s bolt holes. It’s usually expressed in millimeters and consists of two numbers, e.g., 5×112 (5 bolts, 112mm diameter).
Why is it important?
Your wheels must have the correct PCD to fit your car’s hub. If the PCD is incorrect, the wheel simply will not bolt onto your car.
How to find the right PCD:
Check your owner’s manual or online fitment guides.
Popular PCD examples:
- BMW – 5×120 (older models), 5×112 (newer models)
- Audi/VW – 5×112
- Ford – 4×108 or 5×108
Offset (ET) & Why It Matters
What is offset?
Offset (ET) is measured in millimeters and determines how far the wheel sits in or out from the hub.
- Positive Offset (+ET) – Wheels sit closer to the car (e.g., OEM wheels).
- Negative Offset (-ET) – Wheels stick out further, giving a more aggressive stance.
- Neutral Offset (ET0) – The mounting surface is centered in the wheel.
Why is offset important?
- Too high ET? The wheels might sit too far inside, causing clearance issues with suspension components.
- Too low ET? The wheels could poke out too much, leading to rubbing on the arches.
Tip: If your wheels have the wrong offset, spacers can help adjust fitment and come in all different widths.
Wheel Width & Tyre Fitment
How wide should your wheels be?
Wheel width affects how the tyre sits and impacts grip, ride quality, and handling.
- Narrow wheels (7J-8J) – Better fuel efficiency, smoother ride.
- Wide wheels (9J-11J) – More grip and aggressive fitment, but can cause rubbing if not setup correctly.
Tyre Stretch & Fitment:
- A wider wheel than stock may require wider tyres to maintain proper contact.
- Stretching tyres on wide wheels can reduce grip and affect safety so do not do this!
- Ideal tyre fitment varies based on wheel width. Example:
- 8J wheels – 225/40/18 tyres (OEM fitment)
- 9.5J wheels – 255/35/18 tyres
Speedometer Accuracy & Rolling Radius
What is rolling radius?
Rolling radius is the circumference of the tyre, affecting speedometer readings and gearing.
Why does it matter?
- A larger rolling radius makes the speedo under-read as the wheel is rotating slower (e.g., car says 60mph but you’re doing 65mph).
- A smaller rolling radius makes the speedo over-read as the wheel is rotating quicker.
- Maintaining similar overall diameter to stock (within 2-3%) ensures accurate speed readings.
- Have your speedo recalibrated.
💡 Use a tyre size calculator to compare stock vs. aftermarket wheel and tyre sizes.
Clearance & Rubbing Issues
Common clearance problems:
- Suspension interference – If the wheel is too wide or has the wrong offset.
- Arch rubbing – If the wheel is too big or tyres are too wide.
- Brake caliper clearance – Especially important for performance cars with big brakes.
How to avoid rubbing:
- Choose a wheel size that matches factory specifications.
- Use rolling or trimming of the wheel arches if necessary.
- Consider adjustable suspension or camber adjustments for better fitment.
- You may want to fit wheel spacers for a wider track and clearance away from suspension components
Things to consider- If you are running a big brake kit then this will effect the clearance that you have over a stock setup.
Material & Weight Considerations
Alloy vs. Forged Wheels
- Cast Alloy Wheels – Cheaper but heavier. Suitable for daily driving.
- Flow Formed Wheels – Stronger & lighter than cast but not as expensive as fully forged.
- Forged Wheels – Lightweight & ultra-strong, but very expensive. Ideal for performance builds.
Lighter Wheels = Better Performance
- Less weight = better acceleration & handling.
- Lighter wheels reduce unsprung weight, improving suspension performance.
Tip: Consider brands like BBS, OZ Racing, and Rotiform for lightweight options.
Final Tips for Choosing the Right Aftermarket Wheels
- Check your car’s PCD and offset before purchasing.
- Pick a width that suits your tyre setup and won’t cause rubbing.
- Keep rolling radius within 2-3% of OEM size to avoid speedo issues.
- Ensure proper brake clearance, especially for performance cars with bigger brakes.
- Choose lightweight wheels if performance is a priority.