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Project JDM Education

What Is Fitment?

Everything you need to know about wheel offset, backspacing, bolt patterns, and tire sizing before you buy.

WHAT IS FITMENT?

Fitment refers to how a wheel and tire setup physically fits on your car — whether it clears your fenders, suspension, and brakes without rubbing, sits flush or aggressive, and looks the way you want it to look.

Getting fitment right means understanding five key numbers: offset, backspacing, bolt pattern, center bore, and lug size. Get even one of these wrong and your wheels won't bolt on, or they'll rub your fenders at full lock.

WHEEL OFFSET

Offset is the distance in millimeters between the wheel's mounting surface and its centerline. It's the single most important number for how your wheels will look and fit.

Positive Offset
+35mm
Wheel sits further inside the fender. Common on most modern cars and FWD vehicles.
Zero Offset
0mm
Mounting surface exactly at wheel centerline. Common on older vehicles and trucks.
Negative Offset
−15mm
Wheel pushed outward past the fender. Aggressive, wide stance — common in stance builds.
Pro Tip
A 10–15mm change in offset moves your wheel position enough to affect fender clearance, suspension clearance, steering lock, and bearing load. Always check offset before ordering.

BACKSPACING VS OFFSET

Backspacing and offset describe the same thing in two different ways. Backspacing measures the distance from the wheel's mounting surface to the inner lip of the wheel, in inches. Offset measures from the mounting surface to the centerline, in millimeters.

Many wheel spec sheets only list one. Use our Offset & Backspacing Calculator to convert between the two instantly.

BOLT PATTERN

The bolt pattern (also called PCD — Pitch Circle Diameter) tells you how many lug bolts your car has and how far apart they sit. Written as 5x114.3, it means 5 lugs on a 114.3mm circle.

Most Common JDM Bolt Pattern
5x114.3 — Honda, Toyota, Nissan, Acura, Lexus, Infiniti, Ford Mustang. This is the most popular bolt pattern for JDM and sports cars. Most Project JDM wheel inventory fits this pattern.

Use our Bolt Pattern Converter to find compatible vehicles for any bolt pattern.

CENTER BORE

Center bore is the diameter of the center hole on the wheel, in mm. It must match or be larger than your vehicle's hub diameter. If it's too small, the wheel literally won't go on. If it's too large, you'll need hub-centric rings to prevent vibration.

LUG SIZE & TORQUE

Lug nuts come in different thread sizes and seat types. The two most common are M12x1.5 (most Japanese cars) and M14x1.5 (most American/European cars). Always match your lug nuts to your wheel seat type: conical, ball seat, or flat seat.

Lug Nut Torque Specs
M12x1.5: 80–100 ft-lbs  |  M14x1.5: 95–115 ft-lbs  |  Always torque in a star pattern. Re-torque after 50–100 miles.