Bolt Pattern & Hub Bore Checker

Bolt Pattern, PCD, and Center Bore Explained

Three things determine whether a wheel physically mounts to your hub: the lug count, the bolt circle diameter (together written as e.g. 5×120, also called PCD), and the center bore - the machined hole in the middle of the wheel that seats on the hub's center flange.

The Center Bore Rule

• Wheel bore = hub bore - perfect hub-centric fit. OEM wheels are made this way.
• Wheel bore > hub bore - fits, but use hub-centric rings sized exactly (e.g. 74.1 → 72.6). Aftermarket wheels are intentionally bored large to fit many cars; the rings center the wheel so the lugs only clamp.
• Wheel bore < hub bore - does not fit. The wheel can't seat over the hub flange. Machining the bore larger is possible on some wheels but is a job for a wheel shop.

Skipping rings on an oversized bore often causes a highway-speed vibration that wheel balancing can't fix - the wheel is clamped slightly off-center.

Adapters and Wobble Bolts

A different bolt pattern is a hard stop for direct fitment. PCD adapters (e.g. 5×120 car → 5×112 wheels) exist and work when properly torqued, but they add 15-25 mm of effective offset change - run that through the Offset Calculator before committing. "Wobble bolts" cover only tiny PCD differences (≈2 mm) and are controversial; avoid them on track cars.

Measuring a Pattern Yourself

For 4- and 6-lug wheels, measure center-to-center across opposite holes. For 5-lug, measure from the back of one hole to the center of the second-farthest hole - or just count lugs and measure to the nearest known pattern; production patterns are standardized (100, 108, 112, 114.3, 120, 120.65, 130 mm).

Why Patterns Changed on Newer Cars

Note that several manufacturers switched patterns mid-lineage: BMW moved from 5×120 to 5×112 with the G chassis (2019-ish onward), which is why E/F-era wheels don't carry over to a new M3/M4 - and why A90 Supra wheels (BMW-built) are 5×112 too.

Spacers: Hub Engagement and Thread Engagement

A slip-on spacer pushes the wheel away from the hub lip, and the lug bolt or stud loses the same amount of thread. Two rules of thumb cover most situations:

• Hub engagement: if the spacer is thicker than the hub's center lip, the wheel is no longer hub-located ("lug-centric"). Use spacers with their own machined lip, or step up to bolt-on spacers that bolt to the hub and provide a fresh lip.
• Thread engagement: the accepted minimum is engagement equal to the bolt's diameter - for an M12×1.5 bolt that means 12 mm of thread, which is 8 full turns. Count turns when you install: fewer turns than the table says means longer bolts or studs before that wheel sees the road.

With lug bolts (BMW, Porsche, VW), every millimeter of spacer must be matched by a longer bolt. With studs, check that the lug nut still swallows enough thread.