#tire

Tire maths as an API, computed locally and deterministically — the size, pressure and speedometer numbers a driver, fitter or fleet manager works out before fitting a tyre. The size endpoint turns a P-metric spec into the real dimensions: overall diameter = rim + 2 × the sidewall (section width × aspect ratio), so a 225/45R17 stands about 25 inches tall, rolls a 78-inch circumference and turns roughly 808 times a mile — the numbers behind fitment, gearing and clearance. The pressure endpoint gives the hot pressure from a cold pressure and the temperature change, because pressure tracks absolute temperature (P2/P1 = T2/T1), about +1 psi per 10 °F — so 32 psi set cold at 70 °F reads ~34.6 after warming to 100 °F, and drops on a cold morning, which is what trips the warning light. The speedo-error endpoint gives the speedometer error and true speed from a tyre-size change: a taller tyre makes the speedo read low, so actual speed = indicated × new diameter ÷ old — go up 4 % and 60 on the dial is really 62.5. Everything is computed locally and deterministically, so it is instant and private. Ideal for tyre-shop and fitment apps, fleet and 4x4 build tools, speedo-recalibration calculators, and automotive sites. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 compute endpoints. Estimates — always set pressure cold to the placard.

api.oanor.com/tire-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