Gear Ratio

{
  "asOf": "2026-10-12T01:50:57.185Z",
  "cadenceRpm": 90,
  "chainring": 50,
  "circumferenceMm": 2105,
  "cog": 17,
  "degraded": false,
  "developmentMeters": 6.191,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "gearInches": 77.59,
  "metersPerMinute": 557.2,
  "notChecked": [
    "tyre deflection and wear, which change the real circumference by 1 to 2%",
    "crank length (it changes leverage, not speed)",
    "…1 more"
  ],
  "ratio": 2.9412,
  "reasons": [
    "Gear inches = ratio x wheel diameter in inches; development = ratio x wheel circumference."
  ],
  "source": "computed locally (ratio x wheel circumference)",
  "speedKmh": 33.43,
  "speedMph": 20.77,
  "summary": "50/17 is ratio 2.941, 77.6 gear inches, 6.19 m per pedal turn: 33.4 km/h (20.8 mph) at 90 rpm.",
  "verdict": "COMPUTED",
  "wheelDiameterInches": 26.38
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://bike-calc.x402tookit.com/gear-ratio?cadence=90&chainring=50&cog=17&wheel=700x25c'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://bike-calc.x402tookit.com/gear-ratio?cadence=90&chainring=50&cog=17&wheel=700x25c' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fbike-calc.x402tookit.com%2Fgear-ratio
const res = await pay("https://bike-calc.x402tookit.com/gear-ratio?cadence=90&chainring=50&cog=17&wheel=700x25c");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://bike-calc.x402tookit.com/gear-ratio?cadence=90&chainring=50&cog=17&wheel=700x25c")
    print(res.status_code, res.text)