Gear Rpm

{
  "asOf": "2026-10-11T14:38:37.650Z",
  "axleRatio": 3.73,
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "gears": [
    {
      "gear": "1",
      "gearRatio": 3.59,
      "overallRatio": 13.3907,
      "rpm": 10387
    },
    {
      "gear": "2",
      "gearRatio": 2.19,
      "overallRatio": 8.1687,
      "rpm": 6336
    }
  ],
  "notChecked": [
    "torque converter slip in automatics (RPM runs higher until lock-up) and clutch slip",
    "actual loaded tire radius, which is a few percent smaller than nominal diameter",
    "…2 more"
  ],
  "reasons": [
    "Engine RPM = speed (in/min) / tire circumference x gear ratio x axle ratio; the constant is 1056 / pi = 336 for mph and inches."
  ],
  "source": "computed locally",
  "speed": 60,
  "speedMph": 60,
  "speedUnit": "mph",
  "summary": "At 60 mph on a 26 in tire with a 3.73 axle, the engine turns 2401 RPM in gear 5 (overall 3.0959:1).",
  "tireDiameterInches": 26,
  "verdict": "RPM_COMPUTED"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://automotive-calc.x402tookit.com/gear-rpm?axleRatio=3.73&gears=1%3A3.59%3B+2%3A2.19%3B+3%3A1.41%3B+4%3A1.00%3B+5%3A0.83&speed=60&tire=26'

# 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://automotive-calc.x402tookit.com/gear-rpm?axleRatio=3.73&gears=1%3A3.59%3B+2%3A2.19%3B+3%3A1.41%3B+4%3A1.00%3B+5%3A0.83&speed=60&tire=26' \
  | 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%2Fautomotive-calc.x402tookit.com%2Fgear-rpm
const res = await pay("https://automotive-calc.x402tookit.com/gear-rpm?axleRatio=3.73&gears=1%3A3.59%3B+2%3A2.19%3B+3%3A1.41%3B+4%3A1.00%3B+5%3A0.83&speed=60&tire=26");
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://automotive-calc.x402tookit.com/gear-rpm?axleRatio=3.73&gears=1%3A3.59%3B+2%3A2.19%3B+3%3A1.41%3B+4%3A1.00%3B+5%3A0.83&speed=60&tire=26")
    print(res.status_code, res.text)