Calculator
Tire Size & Gear Ratio Calculator
Enter a tire size (285/70R17), differential/final-drive ratio, and transmission gear ratios to compute the true overall tire diameter, circumference, revolutions per mile/km, an RPM × gear speed table, effective final drive after a tire change, and speedometer error. Metric or imperial units, with optional before/after tire comparison.
Quick start
Call this tool from your code in three languages.
curl -X POST 'https://api.elysiatools.com/en/api/tools/tire-gear-ratio-calculator' \
-H 'Content-Type: application/json' \
-d '{"tireSpec":"285/70R17","finalDrive":4.1,"gears":"3.6,2.1,1.4,1,0.8,R3.8","units":"metric","refSpeed":100,"rpmRange":"1000,2000,3000,4000,5000,6000","oldTire":"265/70R17"}'API reference
Send a POST request with your inputs as JSON. File parameters require a separate upload first.
Endpoint
POST https://api.elysiatools.com/en/api/tools/tire-gear-ratio-calculatorParameters
| Name | Type | Required | Description |
|---|---|---|---|
| tireSpec | text | Yes | Full P-metric tire size, e.g. 285/70R17, 265/75R16, 245/45R18. |
| finalDrive | number | Yes | — |
| gears | textarea | Yes | Gear ratios in order; prefix with R for reverse (e.g. R3.8). Comma or newline separated. |
| units | select | No | — |
| refSpeed | number | Yes |
MCP integration
Add this tool to your Model Context Protocol server so AI agents can list and call it.
Server configuration
Add this block to your MCP client configuration:
{
"mcpServers": {
"elysiatools-tire-gear-ratio-calculator": {
"name": "tire-gear-ratio-calculator",
"description": "Enter a tire size (285/70R17), differential/final-drive ratio, and transmission gear ratios to compute the true overall tire diameter, circumference, revolutions per mile/km, an RPM × gear speed table, effective final drive after a tire change, and speedometer error. Metric or imperial units, with optional before/after tire comparison.",
"baseUrl": "https://api.elysiatools.com/mcp/sse?toolId=tire-gear-ratio-calculator",
"command": "",
"args": [],
"env": {},
"isActive": true,
"type": "sse"
}
}
}List available tools
After connecting to the SSE endpoint, list the exposed tools:
{
"jsonrpc": "2.0",
"id": 1,
"method": "tools/list"
}Call this tool
Invoke the tool by its id, passing arguments built from its parameters:
{
"jsonrpc": "2.0",
"id": 2,
"method": "tools/call",
"params": {
"name": "tire-gear-ratio-calculator",
"arguments": {
"tireSpec": "285/70R17",
"finalDrive": 4.1,
"gears": "3.6,2.1,1.4,1,0.8,R3.8",
"units": "metric",
"refSpeed": 100,
"rpmRange": "1000,2000,3000,4000,5000,6000",
"oldTire": "265/70R17"
}
}
}