# Bicycle Gearing & Fit Calc – Cadence for Speed

> Bicycle Gearing & Fit Calc – Cadence for Speed is a paid API for AI agents from bike-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Calculates the cadence needed to hold a target speed in a given gear, or the chainring-to-cog ratio needed to reach a target speed at a given cadence.

## Facts

- Endpoint: GET https://bike-calc.x402tookit.com/cadence-for-speed?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/bicycle-gearing-fit-calc-cadence-for-speed-de2d7b53
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_9YDFcSmXignJQnqNvTJ1j

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability bicycle-gearing-fit-calc-cadence-for-speed-de2d7b53
```

Example prompt: What cadence do I need to hold 30 km/h with a 50-tooth chainring and 17-tooth cog on 700x25c tyres?

## When to prefer this

Use this endpoint when you need to compute cycling cadence or gear ratio for a specific speed target, given a known chainring-cog combination and tyre size. Prefer this over a full drivetrain matrix endpoint when you only need the single-gear cadence or ratio result rather than a comparison across all gears.

## Known failure modes

- Missing required speed parameter (speedKmh or speedMph) returns an error
- Missing chainring or cog teeth when computing cadence causes incomplete results
- Invalid tyre preset string returns an error or falls back to default 700x25c
- Non-positive or zero values for teeth or speed may produce nonsensical results
- Conflicting circumferenceMm and wheel preset — one overrides the other without warning

## How this service works

Cadence needed to hold a target speed in a given gear, and the chainring-to-cog ratio needed for a speed at a cadence.

## Output

Returns the cadence needed (rpm) to hold the target speed in the specified gear, and/or the required chainring-to-cog ratio and development (meters per pedal stroke) to reach the target speed at the given cadence, along with the speed echoed back in both km/h and mph and the rolling circumference used.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [],
     "properties": {
      "cog": {
       "type": "integer",
       "description": "Rear cog teeth"
      },
      "wheel": {
       "type": "string",
       "description": "Tyre preset: 700x23c, 700x25c, 700x28c, 700x32c, 700x35c, 700x38c, 26x2.0 (default 700x25c)"
      },
      "cadence": {
       "type": "number",
       "description": "Cadence in rpm, to get the ratio needed (default 90)"
      },
      "speedKmh": {
       "type": "number",
       "description": "Target speed in km/h (use speedKmh or speedMph)"
      },
      "speedMph": {
       "type": "number",
       "description": "Target speed in mph"
      },
      "chainring": {
       "type": "integer",
       "description": "Chainring teeth, to get the cadence for that gear"
      },
      "circumferenceMm": {
       "type": "number",
       "description": "Rolling circumference in mm instead of a preset"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "cog": {
       "type": [
        "null",
        "number"
       ]
      },
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "speedKmh": {
       "type": [
        "null",
        "number"
       ]
      },
      "speedMph": {
       "type": [
        "null",
        "number"
       ]
      },
      "chainring": {
       "type": [
        "null",
        "number"
       ]
      },

… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/bicycle-gearing-fit-calc-cadence-for-speed-de2d7b53/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from bike-calc.x402tookit.com](https://www.zero.xyz/host/bike-calc.x402tookit.com/llms.txt)