Tyre change: speedo error
API · /tirecalc-api
Tire & Drivetrain 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 health
healthy- Uptime
- 100.00%
- Server probes · 24h
- Avg latency
- 89 ms
- Server probes · 24h
- Subscribers
- 3,070
- active
- Total calls
- 40
- last 7 days
Pricing
Pick a tier — billed monthly, cancel anytime.
Free
Free
- 8,735 calls / month
- 2 requests / second
- Hard cap (429 above quota, no overage)
- 8,735 calls/month
- 2 req/sec
- Tyre + compare + gear
- No credit card
Starter
€10.25 /month
- 18,250 calls / month
- 8 requests / second
- Hard cap (429 above quota, no overage)
- 18.25k calls/month
- 8 req/sec
- Speedometer-error calc
- Email support
Pro
€30.15 /month
- 233,500 calls / month
- 20 requests / second
- Hard cap (429 above quota, no overage)
- 233.5k calls/month
- 20 req/sec
- Automotive / fitment pipelines
- Priority support
Mega
€68.15 /month
- 1,210,000 calls / month
- 50 requests / second
- Hard cap (429 above quota, no overage)
- 1.21M calls/month
- 50 req/sec
- Platform scale
- Dedicated SLA
Built by
Related APIs
Other APIs with overlapping tags.
Gear Ratio API
Gear-train ratio, speed and torque maths as an API, computed locally and deterministically. The ratio endpoint computes the gear ratio of a single pair from the driver and driven tooth counts (or pitch diameters), ratio = N_driven/N_driver, classifies it as a reduction (more torque, less speed) or an overdrive, and — given an input speed and torque — returns the output speed (input/ratio) and the output torque (input·ratio·efficiency). The train endpoint computes a compound gear train: the overall ratio is the product of the individual stage ratios, and it returns each stage ratio, the output speed and torque, noting that idler gears change only the direction of rotation, not the ratio. The solve endpoint finds the missing one of the input speed, the output speed and the ratio from the other two — for example, the ratio needed to drop a 1500 rpm motor to a 500 rpm output. Everything is computed locally and deterministically, so it is instant and private. Ideal for drivetrain, robotics and machine-design tools, gearbox and transmission selection, bicycle and vehicle gearing, and mechanical-engineering education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is gear-train ratio and torque; for spur-gear tooth geometry use a spur-gear API.
api.oanor.com/gearratio-api
Tire Size API
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
Vehicle Braking API
Vehicle-braking physics as an API, computed locally and deterministically. The stopping-distance endpoint computes the total distance to stop a vehicle as the sum of the reaction distance the vehicle travels during the driver's reaction time, v·t, and the braking distance v²/(2·μ·g) — which grows with the square of speed, so doubling the speed quadruples the braking distance — from the speed, the tyre-road friction coefficient, the reaction time and the road grade, along with the deceleration and the time to stop. The braking-force endpoint computes the braking force F = m·a and the deceleration of a vehicle, either from a stop-in-a-given-distance (a = v²/2d) or from the friction coefficient (a = μ·g), with the kinetic energy that must be dissipated as heat. The skid-speed endpoint reconstructs the speed at the start of a skid from the skid-mark length, v = √(2·μ·g·d), a lower-bound estimate used in accident reconstruction. Speed is in km/h by default (also m/s or mph), mass in kg and distances in m; dry asphalt has μ ≈ 0.7, wet ≈ 0.4 and ice ≈ 0.1. Everything is computed locally and deterministically, so it is instant and private. Ideal for automotive, driving-safety, fleet, telematics and accident-reconstruction app developers, stopping-distance and forensic tools, and physics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is vehicle braking; for general kinematics use a kinematics API and for an object on a slope an inclined-plane API.
api.oanor.com/brake-api
Engine Displacement API
Internal-combustion engine maths as an API, computed locally and deterministically. The displacement endpoint computes an engine's swept volume from the bore, the stroke and the number of cylinders, V = (π/4)·bore²·stroke per cylinder, in cubic centimetres, litres and cubic inches, and classifies the bore-to-stroke geometry as oversquare, square or undersquare. The compression endpoint relates the compression ratio and the clearance volume, CR = (swept + clearance)/clearance — give the clearance to get the ratio or the ratio to get the clearance — and, with a boost pressure, estimates the effective compression ratio of a forced-induction engine. The power-to-weight endpoint computes the power-to-weight ratio in horsepower per tonne, kilowatts per tonne and watts per kilogram, the weight per horsepower, and, with a displacement, the specific output in horsepower per litre. Bore and stroke are in millimetres, volumes in cc, weight in kilograms and power in horsepower or kilowatts. Everything is computed locally and deterministically, so it is instant and private. Ideal for automotive, motorsport, motorcycle and engine-builder app developers, build-spec and tuning tools, and mechanical education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is engine geometry and tuning; for EPA fuel-economy data use a fuel-economy API and for tyre sizes a tyre-calculator API.
api.oanor.com/engine-api
Frequently asked questions
Quick answers about pricing, quotas, and integration.
How do I get an API key for Tire & Drivetrain API?
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Code snippets
Sign up to get an API key, then call any path under your slug.
curl https://api.oanor.com/tirecalc-api/SOME_PATH \
-H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/tirecalc-api/SOME_PATH", {
headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/tirecalc-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
"https://api.oanor.com/tirecalc-api/SOME_PATH",
headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())
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