1. Know your bolt pattern & center bore
Every spacer is drilled for one bolt pattern (number of lugs × the diameter of the circle they sit on, e.g. 5x112) and machined for one center bore — the diameter of your hub. Project Fit spacers are hub-centric: the bore matches your hub and a lip on the face matches your wheel, so the wheel stays centered on the hub the way it was from the factory.
The easiest way to get this right is to select your vehicle — we only show spacers with the correct pattern and bore.
2. Choose a thickness
Thickness is per side. A 15mm spacer on each side of an axle widens track width by 30mm total.
- 5mm — fine-tunes flush fitment or clears a big brake kit. May work with factory bolts — check thread engagement (step 4) before driving.
- 10–12.5mm — the most common “flush” step on factory wheels.
- 15mm — a noticeable, aggressive stance on most VW/Audi/BMW/Mercedes platforms.
- 20mm — maximum poke; check fender clearance and suspension travel first.
To measure: with the car on the ground and wheels straight, hold a straightedge vertically against the fender lip and measure to the outer face of the tire. That gap is roughly how much spacer you can add before the tire reaches the fender.
3. Match the lug seat to your wheels
Radius (ball) seat
Rounded seat used by most factory VW, Audi, Mercedes-Benz and Porsche wheels.
Conical (60°) seat
Tapered seat used by most aftermarket wheels and by BMW.
The seat matches your wheel, not your car. Using the wrong seat means the bolt only touches the wheel on a thin line and can loosen. Many Project Fit kits come in both versions — pick Radius for factory wheels and Conical for most aftermarket wheels.
4. Use long enough lug bolts
A spacer pushes the wheel out, so the bolt needs the same amount of extra length. As a rule, thread engagement should be at least equal to the bolt’s diameter — 14mm of engagement (about 9–10 turns) on an M14×1.5 bolt.
New thread length ≈ your factory bolt’s thread length + spacer thickness.
Every Project Fit spacer kit includes 10 bolts already sized for that spacer. If you buy spacers only, add a set of Project Fit lug bolts in your thread, seat and the length above.
5. Install & re-torque
- Clean rust and debris from the hub face and the back of the wheel.
- Slide the spacer onto the hub; it should sit completely flat.
- Mount the wheel and snug the bolts in a star pattern.
- Torque to your manufacturer’s spec with a torque wrench, not an impact gun.
- Re-torque after the first 50 miles.