#speedometer

Tyre-size geometry as an API, computed locally and deterministically. The dimensions endpoint parses a metric tyre code such as 205/55R16 — or separate width, aspect ratio and rim values — into its full geometry: the sidewall height (width·aspect/100), the overall diameter (rim·25.4 + 2·sidewall) in millimetres and inches, the rolling circumference, and the revolutions per kilometre and per mile; a 205/55R16 works out to a 112.75 mm sidewall and a 631.9 mm (24.88 in) outside diameter. The compare endpoint takes an original and a replacement size and computes the speedometer error and ground-clearance change of swapping between them: because the speedometer is calibrated to the original rolling diameter, a larger tyre makes it read low, so true speed = indicated · OD_new/OD_old, and a tyre that is 2 % bigger means an indicated 100 is really about 102 km/h. Staying within ±3 % keeps the error and clearance change small. Tyre codes use the metric P-metric/Euro-metric form. Everything is computed locally and deterministically, so it is instant and private. Ideal for automotive, tyre-shop, fitment, car-enthusiast, fleet and vehicle-spec app developers, plus-sizing and speedo-error tools, and garage software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 2 endpoints. This is metric tyre geometry; for fuel economy use a fuel-economy API.

api.oanor.com/tiresize-api

Tyre, wheel and drivetrain maths as an API. The tire endpoint parses a metric tyre size such as 205/55R16 into all its real dimensions — section width, aspect ratio, sidewall height, rim and overall diameter in millimetres and inches, rolling circumference, and revolutions per kilometre and per mile. The compare endpoint takes an original and a replacement tyre size and works out the change in overall diameter and the resulting speedometer and odometer error — so you know how much faster you are really going than the dial shows after a tyre change. The gear endpoint computes a gear ratio from ring and pinion tooth counts, or the road speed from engine RPM, total gear ratio and tyre size. Everything is computed locally and deterministically, so it is instant and private. Ideal for automotive and motorsport apps, tyre shops and fitment tools, modding and restomod planning, and vehicle configurators. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is tyre and drivetrain maths; for vehicle specifications by VIN use a vehicle-database API.

api.oanor.com/tirecalc-api