Wheel and tyre tools
Free calculators, with no account needed, to understand your car's measurements and compare two set-ups before you choose. They compare; they never recommend a measurement: the offset and width of a wheel are worked out for each car and its brakes.
Calculators
- Tyre size calculator: compare two tyre sizes: diameter, sidewall, circumference, speedometer difference and the ETRTO tolerance, with a table of equivalent sizes from 15 to 24 inches.
- Wheel offset calculator: compare your current set-up with another (width, offset (ET), spacer): how far the wheel moves out towards the arch and in towards the suspension, to the millimetre.
Fitment data
Our fitment data is published in French, with every measurement sourced:
- PCD by car: every bolt pattern and the cars that share it (page in French).
- Open atlas of original wheel measurements (page in French): PCD, centre bore, diameter, width, original offset and tyre size for every generation we cover, also as a CSV file free to reuse under CC BY 4.0.
Guides
- What size wheels fit my car? How to find your wheel size
- What is wheel offset (ET)? Positive, zero and negative
- How to read a tyre size (and the load and speed index)
- PCD, bolt pattern and centre bore: how a wheel fits a car
- Wheel spacers explained: how they work, safety and the law
- Hub-centric rings and centre bore: do you need them?
Your custom forged wheel project: design it.