Wheel fitment guide
Five measurements decide whether a wheel and tyre fit. Two are pass-or-fail. Three are a matter of clearance, and those are the ones worth modelling before you buy.
The pass-or-fail pair
Bolt pattern (PCD) is the number of studs and the circle they sit on, written as 5x112 or 4x100. It either matches or it does not — there is no near-enough. Centre bore is the hole in the middle: it must be at least as large as the hub, and any gap is taken up with a spigot ring so the wheel centres on the hub rather than hanging on the bolts.
Both of these are specific to your vehicle. Get them from the vehicle handbook, the existing wheel, or a supplier who confirms against your registration — not from a general chart.
The three that need measuring
Rim diameter must match the tyre exactly, and going up a size usually means a lower-profile tyre to hold rolling diameter steady. See the rim size chart.
Rim width has a usable range per tyre width — see the tyre width chart — and adds 12.7 mm per side for each extra inch.
Offset moves the whole wheel in or out, one millimetre per millimetre. See wheel offset explained.
The five measurements at a glance
| Measurement | Units | Tolerance | Where to find it |
|---|---|---|---|
| Bolt pattern (PCD) | Count × mm | Exact match only | Handbook or existing wheel |
| Centre bore | mm | Equal or larger, ring the gap | Measure the hub |
| Rim diameter | inches | Must match the tyre exactly | Stamped on the wheel |
| Rim width | inches | Range per tyre width | Stamped, e.g. 7.5J |
| Offset (ET) | mm | Limited by clearance | Stamped, e.g. ET45 |
The order to check in
- Confirm bolt pattern and centre bore. If either is wrong, nothing else matters.
- Choose rim diameter, then a tyre that keeps rolling diameter within about 1%.
- Check the tyre width suits the rim width.
- Model the offset change and check inner clearance against the strut and outer against the arch.
- Measure the car. Turn the steering lock to lock and compress the suspension if you can.
What the numbers cannot tell you
Geometry gets you close, but arch shape, liner position, suspension travel and how much the car is lowered all vary. Every calculated figure is a starting point for a physical check, never a substitute for one.
Model a change on the fitment calculator, or start from a tyre size comparison.
Related
How are these fitment figures calculated?
Fitment North calculates declared wheel and tyre geometry from the dimensions shown on the page, using the same tested method as the wheel-offset and tyre-size calculator. Tyre diameter uses rim diameter plus two calculated sidewalls; offset comparisons split width changes across inner and outer edges before applying the offset difference. Results are measurement aids, not vehicle approval. Confirm ratings, clearances and manufacturer guidance before fitting parts.