How it works

A wheel's bolt pattern is specified as [lug count]×[PCD in mm], e.g. 6×139.7. The PCD (Pitch Circle Diameter) is the diameter of the imaginary circle that passes through the centre of all lug holes. Both the lug count and the PCD must match exactly — a wheel with the right lug count but wrong PCD will not seat properly on the hub, and will shear studs under load.

Some bolt patterns are expressed in imperial (e.g. 6×5.5" = 6×139.7mm). We normalise everything to metric in the database so searching always works.

Bolt adapters can bridge mismatched patterns (e.g. 5×127 Jeep to 5×139.7 Toyota). We flag when a reputable adapter exists, but only from forged-billet hub-centric brands — not import-quality unbranded pieces.

Every hub has a centre spigot of a specific diameter. The wheel's centre bore must be equal to or larger than the hub bore. If the wheel bore is smaller, it physically cannot seat and the wheel will not fit.

If the wheel bore is larger than the hub bore, the wheel is lug-centric — it centres on the studs rather than the hub. This causes vibration at highway speeds and, over time, fatigue in the studs. A hub-centric ring fills the gap (typically $5–15 per set) and restores proper hub-centric loading. We flag when a ring is needed and link to where to buy one.

Offset is the distance in millimetres between the wheel's hub face and its centreline. Positive offset pushes the wheel inboard (tucked); negative pushes it outboard (poked/stretched).

Changing offset has three effects:

• Clearance: Too much negative offset (wheel pushed outboard) causes tyre-to-fender rub and may fail roadworthy inspections in some states.
• Ball joint stress: Each millimetre of outboard offset adds leverage on the upper ball joint. Off-road use amplifies this.
• Track width: Wider track improves stability but may require guards for legal compliance in AU (max 25mm each side in most states) and some US states.

We calculate a safe offset window for each chassis based on factory offset and common community experience. Wheels outside the window get an amber warning — not a block.

Lift kits raise the body away from the axles, creating more space for larger tires. The relationship is roughly linear for the first few inches but becomes non-linear beyond 3" because you're fighting CV angles, diff geometry, and steering component limits.

Our chassis data includes a stock tire ceiling (max diameter without rubbing at full articulation) and a lifted ceiling (the typical maximum with 2–3" of lift and no body modifications). We calculate exact clearance at each lift increment and flag when you'll need fender trimming, UCA upgrades, or body lifts to go further.

A bolt adapter is a machined plate that bolts to your vehicle's hub and presents a different bolt pattern (and often wider track) to the wheel. Done right, they are safe. Done wrong, they fail catastrophically.

The minimum bar for a safe adapter:

• Forged or billet alloy — not cast or welded
• Hub-centric on both sides — the adapter must centred on your hub, and the wheel must centre on the adapter
• Correct torque spec — both inner and outer studs to manufacturer spec, re-torqued after 50 km
• Reputable brand — Spidertrax, TeraFlex, Gorilla, H&R, McGard. Not unbranded eBay stock

We only surface adapters from brands that meet these criteria, and we never recommend cross-lug-count adapters (e.g. 5-lug to 6-lug) without a clear safety note.

Every fitment fact has a confidence tier that reflects how well the claim is corroborated. We use four tiers: