Black anodised hub-centric wheel spacer fitted to vehicle

How to Measure for the Perfect Wheel Spacer Size

Choosing the right wheel spacer size can completely transform your car’s stance and handling — but only if you measure correctly. Too small, and you won’t get the look or clearance you want. Too large, and you risk rubbing issues, poor fitment, or unsafe wheel installation.

This guide walks you through exactly how to measure for the perfect wheel spacer size, using simple steps and tools you likely already have.

Why Wheel Spacer Size Matters

Before diving into the measurements, it's important to understand why spacer sizing is so crucial:

  • Improves stance by pushing wheels outward for a wider, more aggressive look

  • Boosts handling by widening the track width

  • Corrects clearance issues with brakes, suspension, or arch liners

  • Ensures proper fitment so the wheels sit flush with your arches

Getting the size wrong undermines all of these benefits — so accurate measurement is key.

What You’ll Need

You don’t need anything fancy. These basic tools will do the job:

  • A straight edge (ruler or metal bar)

  • A measuring tape or vernier caliper

  • A flat surface

  • Your current wheels fitted to the car

Step-by-Step: How to Measure Wheel Spacer Size

1. Park on Flat, Level Ground

This ensures your wheels sit naturally in their arches. Uneven ground can skew measurements by several millimetres.

2. Identify Your Fitment Goal

What are you trying to achieve?

Typical reasons:

  • Flush fitment (wheel in line with outer arch)

  • Aggressive stance (slightly poking outward)

  • Brake clearance (wheel fouling on calipers)

  • Suspension clearance (tyre rubbing struts or shocks)

Your measurement may differ slightly depending on the goal.

3. Measure the Gap to the Wheel Arch

This is the simplest and most accurate method for stance and flush fitment.

How to do it:

  1. Place a straight edge vertically against the wheel arch.

  2. Measure the distance between the straight edge and the wheel’s outer sidewall.

This measurement is typically between 5mm and 25mm.

Example:

  • Distance from arch to wheel: 15mm
    → A 15mm spacer will make the wheel sit flush.

If you want slight poke, add 2–3mm.

4. Check Inside Clearance (If Needed)

If your wheel is hitting the brake caliper or suspension, measure the inside gap:

  1. Remove the wheel.

  2. Hold the wheel in front of the hub as if it were bolted on.

  3. Measure the closest point between:

    • Wheel barrel → brake caliper

    • Tyre → suspension strut

If you need more clearance, choose a spacer that meets or exceeds that gap.

Example:

  • Caliper clearance needed: 5mm
    → Minimum spacer size: 5mm or larger

5. Consider Wheel Offset (ET)

If you know your current wheel offset (ET), you can calculate ideal spacer size mathematically.

Formula:

New Offset = Current Offset – Spacer Thickness

Example:

  • Current offset: ET45

  • Spacer: 15mm

New offset = 45 – 15 = ET30

Most cars look flush between ET25–ET35 (varies by model).

6. Cross-Check Both Front and Rear

Cars often have different arch shapes front and rear, so measure both separately.

It’s common to run:

  • Front: 10mm

  • Rear: 15–20mm

Mixing sizes is perfectly normal.

7. Choose Hub-Centric Spacers

Once you know your exact size, choose hub-centric spacers for safety and vibration-free driving.

Avoid universal or “floating” spacers — they often cause wobble and poor fitment.

Recommended Spacer Sizes (General Guide)

These are typical averages — always measure your own car.

Hot hatches:

  • Front: 10–12mm

  • Rear: 15–20mm

German saloons (Audi/BMW/Mercedes):

  • Front: 10–15mm

  • Rear: 15–25mm

Sports cars:

  • Front: 5–10mm

  • Rear: 10–15mm

Common Measurement Mistakes (and How to Avoid Them)

Guessing or eyeballing

Always use tools — even a ruler is better than guessing.

Not measuring both sides

Cars aren’t perfectly symmetrical; measure each side.

Forgetting tyre stretch or camber

Aggressive setups change where the tyre sits.

Choosing the spacer size you wish you could run

Choose the correct size, not the biggest one.

Final Thoughts

Measuring for wheel spacers is simple — but getting it right is crucial. With just a straight edge and a measuring tape, you can determine the perfect size for:

  • Better stance

  • Improved handling

  • Correct wheel fitment

  • Safe, vibration-free driving

When in doubt: measure twice, choose once.

Looking to fit spacers to your vehicle? Click here to find spacers that fit your vehicle.

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