Get alternative wheel and tire sizes derived from the OE size

Returns rim and tire combinations geometrically compatible with an original equipment (OE) wheel: tire sizes from a static ISO 4000-1 metric size catalogue whose design tyre section width (S) and design overall diameter (Do) stay within the given tolerances of the OE tire, on each rim diameter from steps_min to steps_max around the OE diameter.

The row for the OE size echoes the requested rim. For every other candidate the rim width is the tire's measuring rim width code (Rmc, ISO 4000-1, rounded to the nearest 0.5"), and the offset is adjusted to keep the OE scrub radius (kingpin offset at ground), assuming a steering-axis inclination of 18° and a camber angle of +2° (top of the wheel leaning outward).

Market availability, load index, speed symbol, and brake or suspension clearance are not checked — confirm fitment on the vehicle.

Demo: Rim & Tire Size Calculator — https://www.wheel-size.com/calc/

Parameters:

• OE rim: rim_diameter, rim_width, rim_offset — e.g. 17 ⨯ 7J ET45
• OE tire: section_width, aspect_ratio — e.g. 225/55 R17
• Rim diameter range: steps_min (-3 to 0, default 0) and steps_max (0 to 3, default 2) are the lowest and highest 1-inch steps relative to the OE diameter; the OE diameter (step 0) is always included, so steps_min=-1&steps_max=2 returns 17–20" for an 18" OE wheel. Half-inch diameters (e.g. 17.5) are included where catalogued, with the step of their integer part.
• Deprecated: steps (-3 to 3) sets one direction only: steps=n (n > 0) = steps_max=n; steps=-n = steps_min=-n&steps_max=0; steps=0 = steps_max=0. It cannot be combined with steps_min / steps_max.
• Tolerances (inclusive): s_max — design section width, 0–25 %, default 10 %; do_max — design overall diameter, 0–15 %, default 5 %.

Response:

• Rows are ordered by rim diameter, rim width and overall diameter difference; exactly one row has is_oe=true.
• step on every row; meta.by_diameter lists every enumerated rim diameter with its step and row count (including diameters where nothing fits); meta.by_rim counts rows per rim designation.

References:

• ISO 4000-1:2015 Passenger car tyres and rims — Part 1: Tyres (metric series)
• ISO 4000-2 Passenger car tyres and rims — Part 2: Rims
• ISO 8855 Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary