Bolt pattern
The lug count and PCD diameter that determine which wheels can physically bolt to a vehicle hub.
A bolt pattern is written as [lug count] × [PCD in mm] — for example 6×139.7 is six lugs on a 139.7 mm Pitch Circle Diameter. Both numbers must match exactly. A wheel with the right lug count but the wrong PCD will not seat properly on the hub and will shear studs under load.
Some bolt patterns are quoted in inches (6×5.5″ = 6×139.7 mm). FitsMyRig normalises everything to metric so search results stay consistent.
Bolt-pattern adapters can bridge mismatches (for example 5×127 Jeep to 5×139.7 Toyota), but only forged-billet, hub-centric, brand-name adapters from Spidertrax / TeraFlex / Gorilla / McGard / H&R should be used.
See also
PCD (Pitch Circle Diameter)
The diameter of the imaginary circle that passes through the centre of every lug hole on a wheel hub.
Hub-centric ring
A small ring that fills the gap between an oversized wheel centre bore and a smaller hub spigot, restoring centric loading.
Bolt adapter
A machined plate that bolts to a vehicle hub and presents a different bolt pattern (and often wider track) to the wheel.