CheckFitment MCP
Provides read-only tools for vehicle wheel and tire fitment calculations, including bolt pattern lookups, wheel spacer sizing, gear ratio changes, and tire size comparisons using the CheckFitment dataset.
Endpoint and access
No sign-in to connect and list tools. Individual tools may still need a vendor account, credentials, or permissions; check the documented prerequisites.
MCP endpoint (Streamable HTTP)
https://checkfitment.com/mcp?src=mcpWhat you can do with it
- Lookup vehicle bolt patterns and wheel specs
- Calculate wheel spacer size and stud engagement
- Determine gear ratio changes after tire size modifications
- Compare tire sizes for speedometer error and diameter changes
Source and maintenance
Vendor evidenceRegistry 1.1.0
Protocol and capabilities
- Server
- checkfitment 1.1.0
- MCP protocol
- 2025-06-18
- Tools
- 6 advertised
- Resources
- Not advertised
- Resource templates
- Not advertised
- Prompts
- Not advertised
Server-advertised capabilities
{
"tools": {
"listChanged": false
}
}Server-provided instructions
Untrusted server output shown for inspection. It is not Koskamo guidance and is excluded from knowledge search.
Tools
6 advertised
bolt_pattern_lookup — Vehicle bolt pattern and wheel specs
Advertised read-only
Use for "what is the bolt pattern on a 2019 Ford F-150", lug torque, center bore, thread size, OEM wheel size, offset or tire size of a vehicle, or "will these wheels fit my car" when the vehicle is named. Looks the vehicle up in the CheckFitment dataset (a fixed set of vehicles, each spec cited to manufacturer documents and marked verified or unverified). If the vehicle or year is not in the dataset the tool says so (not_in_database / year_covered false) and gives no figures; never fill them in from memory. Optional wheel_center_bore_mm runs the hub-centric check.
bolt_pattern_lookup input schema
{
"type": "object",
"required": [
"make",
"model"
],
"properties": {
"make": {
"type": "string",
"description": "e.g. Ford, Toyota, Jeep"
},
"year": {
"type": "integer",
"maximum": 2030,
"minimum": 1950
},
"model": {
"type": "string",
"description": "e.g. F-150, Tacoma, Wrangler"
},
"wheel_center_bore_mm": {
"type": "number",
"description": "Optional: center bore of a wheel you want to check against the hub."
}
},
"additionalProperties": false
}bolt_pattern_lookup output schema
{
"type": "object",
"required": [
"not_in_database",
"generations",
"link",
"disclaimer"
],
"properties": {
"link": {
"type": "string"
},
"make": {
"type": [
"string",
"null"
]
},
"year": {
"type": [
"number",
"null"
]
},
"model": {
"type": "string"
},
"patterns": {
"type": "array",
"items": {
"type": "string"
}
},
"ambiguous": {
"type": "boolean"
},
"candidates": {
"type": "array",
"items": {
"type": "string"
}
},
"disclaimer": {
"type": "string"
},
"generations": {
"type": "array",
"items": {
"type": "object",
"required": [
"years",
"bolt_pattern_mm",
"bolt_pattern_in",
"verified",
"sources"
],
"properties": {
"trim": {
"type": [
"string",
"null"
]
},
"notes": {
"type": [
"string",
"null"
]
},
"years": {
"type": "string"
},
"thread": {
"type": [
"string",
"null"
]
},
"sources": {
"type": "array",
"items": {
"type": "object",
"required": [
"type",
"ref"
],
"properties": {
"ref": {
"type": "string"
},
"url": {
"type": [
"string",
"null"
]
},
"type": {
"type": "string"
}
}
}
},
"fastener": {
"type": "string"
},
"verified": {
"type": "boolean"
},
"oem_tires": {
"type": "array",
"items": {
"type": "string"
}
},
"confidence": {
"type": [
"string",
"null"
]
},
"generation": {
"type": [
"string",
"null"
]
},
"oem_offset": {
"type": "string"
},
"oem_wheels": {
"type": "array",
"items": {
"type": "string"
}
},
"fastener_note": {
"type": [
"string",
"null"
]
},
"lug_torque_nm": {
"type": [
"number",
"null"
]
},
"center_bore_mm": {
"type": [
"number",
"null"
]
},
"bolt_pattern_in": {
"type": "string"
},
"bolt_pattern_mm": {
"type": "string"
},
"lug_torque_lbft": {
"type": [
"number",
"null"
]
},
"lug_torque_note": {
"type": [
"string",
"null"
]
},
"lug_torque_text": {
"type": [
"string",
"null"
]
},
"lug_torque_steel_lbft": {
"type": [
"number",
"null"
]
}
}
}
},
"lug_sequence": {
"type": [
"array",
"null"
],
"items": {
"type": "integer"
}
},
"year_covered": {
"type": "boolean"
},
"models_for_make": {
"type": "array",
"items": {
"type": "string"
}
},
"not_in_database": {
"type": "boolean"
},
"years_in_dataset": {
"type": "string"
},
"center_bore_check": {
"type": [
"object",
"null"
],
"properties": {
"ring": {
"type": [
"string",
"null"
]
},
"gap_mm": {
"type": "number"
},
"hub_mm": {
"type": "number"
},
"status": {
"type": "string"
},
"wheel_bore_mm": {
"type": "number"
}
}
},
"makes_in_database": {
"type": "array",
"items": {
"type": "string"
}
},
"lookalike_patterns": {
"type": "array",
"items": {
"type": "object",
"properties": {
"tier": {
"type": "string"
},
"gap_mm": {
"type": "number"
},
"pattern": {
"type": "string"
},
"lookalike": {
"type": "string"
}
}
}
},
"specs_differ_between_candidates": {
"type": "boolean"
}
}
}bolt_pattern_lookup annotations
{
"title": "Vehicle bolt pattern and wheel specs",
"readOnlyHint": true,
"openWorldHint": false,
"idempotentHint": true,
"destructiveHint": false
}wheel_fitment_check — Will these wheels (and tires) fit
Advertised read-only
Use to compare a current wheel (and tire) with a new one: how far the outer edge pokes toward the fender and the inner edge toward the suspension, the diameter and ride-height change, speedometer effect, backspacing, and whether the new tire width suits the new rim width. With measured clearances (outer: tire edge to fender lip; inner: to the nearest suspension part, both on the current setup) it returns fits / tight / rub. Leave the tire fields out for a wheel-only offset comparison.
wheel_fitment_check input schema
{
"type": "object",
"required": [
"current_wheel_width_in",
"current_offset_mm",
"new_wheel_width_in",
"new_offset_mm"
],
"properties": {
"new_tire": {
"type": "string",
"description": "New tire size. Metric like 265/70R17 (P or LT prefix allowed) or flotation like 33x12.50R17; no load index or speed rating."
},
"current_tire": {
"type": "string",
"description": "Current tire size. Metric like 265/70R17 (P or LT prefix allowed) or flotation like 33x12.50R17; no load index or speed rating."
},
"new_offset_mm": {
"type": "number",
"maximum": 100,
"minimum": -100
},
"current_offset_mm": {
"type": "number",
"maximum": 100,
"minimum": -100
},
"inner_clearance_mm": {
"type": "number",
"minimum": 0,
"description": "Measured on the current setup: inner sidewall to the nearest suspension or body part."
},
"new_wheel_width_in": {
"type": "number",
"maximum": 16,
"minimum": 4
},
"outer_clearance_mm": {
"type": "number",
"minimum": 0,
"description": "Measured on the current setup: tire sidewall to fender lip."
},
"current_wheel_width_in": {
"type": "number",
"maximum": 16,
"minimum": 4
}
},
"additionalProperties": false
}wheel_fitment_check output schema
{
"type": "object",
"required": [
"mode",
"poke_out_mm",
"inner_in_mm",
"backspacing_old_in",
"backspacing_new_in",
"link",
"disclaimer"
],
"properties": {
"new": {
"type": "object"
},
"link": {
"type": "string"
},
"mode": {
"enum": [
"wheel_only",
"wheel_and_tire"
],
"type": "string"
},
"current": {
"type": "object"
},
"verdict": {
"type": [
"string",
"null"
]
},
"disclaimer": {
"type": "string"
},
"inner_in_mm": {
"type": "number"
},
"poke_out_mm": {
"type": "number"
},
"tire_on_rim": {
"type": "object",
"properties": {
"note": {
"type": "string"
},
"status": {
"type": "string"
},
"max_rim_in": {
"type": "number"
},
"min_rim_in": {
"type": "number"
},
"ideal_rim_in": {
"type": "number"
},
"effective_tread_width_mm": {
"type": "number"
}
}
},
"inner_verdict": {
"type": [
"string",
"null"
]
},
"outer_verdict": {
"type": [
"string",
"null"
]
},
"center_shift_mm": {
"type": "number"
},
"shown_at_true_60": {
"type": "number"
},
"inner_edge_set_by": {
"type": "string"
},
"outer_edge_set_by": {
"type": "string"
},
"backspacing_new_in": {
"type": "number"
},
"backspacing_old_in": {
"type": "number"
},
"diameter_change_in": {
"type": "number"
},
"diameter_change_mm": {
"type": "number"
},
"ride_height_change_mm": {
"type": "number"
},
"inner_clearance_left_mm": {
"type": [
"number",
"null"
]
},
"outer_clearance_left_mm": {
"type": [
"number",
"null"
]
},
"speedometer_reads_low_pct": {
"type": "number"
}
}
}wheel_fitment_check annotations
{
"title": "Will these wheels (and tires) fit",
"readOnlyHint": true,
"openWorldHint": false,
"idempotentHint": true,
"destructiveHint": false
}tire_size_compare — Tire size change: diameter and speedometer
Advertised read-only
Use for "what changes if I go from 265/70R17 to 285/75R17", "how far off is my speedometer with 33s", or odometer error after a tire change. Returns diameter, width, sidewall and ride-height change, the true speed when the speedometer shows a given value, the odometer error and how serious it is.
tire_size_compare input schema
{
"type": "object",
"required": [
"old_tire",
"new_tire"
],
"properties": {
"new_tire": {
"type": "string",
"description": "New tire. Metric like 265/70R17 (P or LT prefix allowed) or flotation like 33x12.50R17; no load index or speed rating."
},
"old_tire": {
"type": "string",
"description": "Factory or current tire. Metric like 265/70R17 (P or LT prefix allowed) or flotation like 33x12.50R17; no load index or speed rating."
},
"speed_shown": {
"type": "number",
"maximum": 200,
"minimum": 1,
"description": "Speedometer reading to convert (default 60)."
}
},
"additionalProperties": false
}tire_size_compare output schema
{
"type": "object",
"required": [
"old_tire",
"new_tire",
"diameter_change_pct",
"true_speed_at_shown",
"severity",
"link",
"disclaimer"
],
"properties": {
"link": {
"type": "string"
},
"new_tire": {
"type": "object",
"properties": {
"size": {
"type": "string"
},
"diameter_in": {
"type": "number"
},
"diameter_mm": {
"type": "number"
},
"sidewall_mm": {
"type": "number"
},
"section_width_mm": {
"type": "number"
}
}
},
"old_tire": {
"type": "object",
"properties": {
"size": {
"type": "string"
},
"diameter_in": {
"type": "number"
},
"diameter_mm": {
"type": "number"
},
"sidewall_mm": {
"type": "number"
},
"section_width_mm": {
"type": "number"
}
}
},
"severity": {
"type": "string"
},
"disclaimer": {
"type": "string"
},
"speed_shown": {
"type": "number"
},
"severity_note": {
"type": "string"
},
"width_change_mm": {
"type": "number"
},
"diameter_change_in": {
"type": "number"
},
"odometer_error_pct": {
"type": "number"
},
"diameter_change_pct": {
"type": "number"
},
"true_speed_at_shown": {
"type": "number"
},
"ride_height_change_in": {
"type": "number"
}
}
}tire_size_compare annotations
{
"title": "Tire size change: diameter and speedometer",
"readOnlyHint": true,
"openWorldHint": false,
"idempotentHint": true,
"destructiveHint": false
}wheel_spacer_calculator — Wheel spacer size and stud engagement
Advertised read-only
Use for "do I need spacers", "what spacer gets +35 wheels to +20", "is a 10 mm slip-on spacer safe". A spacer lowers the effective offset by its thickness. Returns the spacer needed for a target offset (and the nearest common size), the effective offset, track change, whether it is slip-on or bolt-on territory, and, with stud, stud_protrusion_mm and wheel_pad_thickness_mm, the slip-on thread-engagement check (≥ 1 × stud diameter and ≥ 6.5 turns).
wheel_spacer_calculator input schema
{
"type": "object",
"required": [
"offset_mm"
],
"properties": {
"stud": {
"enum": [
"M12x1.5",
"M12x1.25",
"M14x1.5",
"M14x2.0",
"1/2-20",
"9/16-18",
"7/16-20"
],
"type": "string"
},
"offset_mm": {
"type": "number",
"maximum": 100,
"minimum": -100,
"description": "Offset (ET) of the wheel."
},
"spacer_mm": {
"type": "number",
"maximum": 100,
"minimum": 0
},
"target_offset_mm": {
"type": "number",
"maximum": 100,
"minimum": -100
},
"stud_protrusion_mm": {
"type": "number",
"minimum": 0,
"description": "Stud length past the hub face."
},
"wheel_pad_thickness_mm": {
"type": "number",
"minimum": 0,
"description": "Thickness of the wheel mounting pad."
}
},
"additionalProperties": false
}wheel_spacer_calculator output schema
{
"type": "object",
"required": [
"offset_mm",
"link",
"disclaimer"
],
"properties": {
"link": {
"type": "string"
},
"offset_mm": {
"type": "number"
},
"spacer_mm": {
"type": [
"number",
"null"
]
},
"disclaimer": {
"type": "string"
},
"engagement": {
"type": [
"object",
"null"
],
"properties": {
"safe": {
"type": "boolean"
},
"stud": {
"type": "string"
},
"min_mm": {
"type": "number"
},
"min_turns": {
"type": "number"
},
"turns_after": {
"type": "number"
},
"engaged_after_mm": {
"type": "number"
},
"engaged_before_mm": {
"type": "number"
},
"extra_stud_length_needed_mm": {
"type": "number"
}
}
},
"spacer_type": {
"type": [
"string",
"null"
]
},
"moves_out_mm": {
"type": [
"number",
"null"
]
},
"spacer_needed": {
"type": [
"object",
"null"
],
"properties": {
"exact_mm": {
"type": "number"
},
"possible": {
"type": "boolean"
},
"nearest_common_mm": {
"type": [
"number",
"null"
]
}
}
},
"track_change_mm": {
"type": [
"number",
"null"
]
},
"target_offset_mm": {
"type": [
"number",
"null"
]
},
"effective_offset_mm": {
"type": [
"number",
"null"
]
}
}
}wheel_spacer_calculator annotations
{
"title": "Wheel spacer size and stud engagement",
"readOnlyHint": true,
"openWorldHint": false,
"idempotentHint": true,
"destructiveHint": false
}gear_ratio_calculator — Gear ratio after a tire change, regear
Advertised read-only
Use for "what does my 3.73 axle behave like on 35s", "what ratio do I need to regear for 33s", RPM at highway speed after a tire change, or the crawl ratio (with transfer-case low ratio and first gear). Returns the effective ratio, RPM before and after in a 1:1 gear, the ratio that restores stock feel, the nearest gear set actually sold and how serious the change is.
gear_ratio_calculator input schema
{
"type": "object",
"required": [
"old_tire",
"new_tire",
"axle_ratio"
],
"properties": {
"new_tire": {
"type": "string",
"description": "New tire. Metric like 265/70R17 (P or LT prefix allowed) or flotation like 33x12.50R17; no load index or speed rating."
},
"old_tire": {
"type": "string",
"description": "Factory tire. Metric like 265/70R17 (P or LT prefix allowed) or flotation like 33x12.50R17; no load index or speed rating."
},
"speed_mph": {
"type": "number",
"maximum": 150,
"minimum": 1,
"description": "Road speed for the RPM figures (default 65)."
},
"axle_ratio": {
"type": "number",
"maximum": 8,
"minimum": 1.5,
"description": "Current axle (differential) ratio, e.g. 3.73."
},
"first_gear_ratio": {
"type": "number",
"maximum": 10,
"minimum": 1
},
"transfer_case_low_ratio": {
"type": "number",
"maximum": 10,
"minimum": 1
}
},
"additionalProperties": false
}gear_ratio_calculator output schema
{
"type": "object",
"required": [
"axle_ratio",
"effective_ratio",
"regear_ratio_to_restore",
"nearest_stock_ratio",
"link",
"disclaimer"
],
"properties": {
"link": {
"type": "string"
},
"crawl": {
"type": [
"object",
"null"
],
"properties": {
"rating": {
"type": "string"
},
"rating_note": {
"type": "string"
},
"with_current_axle": {
"type": "number"
},
"with_nearest_regear": {
"type": "number"
}
}
},
"new_tire": {
"type": "object",
"properties": {
"size": {
"type": "string"
},
"diameter_in": {
"type": "number"
},
"diameter_mm": {
"type": "number"
},
"sidewall_mm": {
"type": "number"
},
"section_width_mm": {
"type": "number"
}
}
},
"old_tire": {
"type": "object",
"properties": {
"size": {
"type": "string"
},
"diameter_in": {
"type": "number"
},
"diameter_mm": {
"type": "number"
},
"sidewall_mm": {
"type": "number"
},
"section_width_mm": {
"type": "number"
}
}
},
"severity": {
"type": "string"
},
"speed_mph": {
"type": "number"
},
"axle_ratio": {
"type": "number"
},
"disclaimer": {
"type": "string"
},
"severity_note": {
"type": "string"
},
"effective_ratio": {
"type": "number"
},
"diameter_change_pct": {
"type": "number"
},
"nearest_stock_delta": {
"type": "number"
},
"nearest_stock_ratio": {
"type": "number"
},
"regear_ratio_to_restore": {
"type": "number"
},
"rpm_new_at_speed_direct_drive": {
"type": "number"
},
"rpm_old_at_speed_direct_drive": {
"type": "number"
}
}
}gear_ratio_calculator annotations
{
"title": "Gear ratio after a tire change, regear",
"readOnlyHint": true,
"openWorldHint": false,
"idempotentHint": true,
"destructiveHint": false
}bolt_pattern_facts — Bolt pattern in mm and inches, look-alikes
Advertised read-only
Use for "what is 5x114.3 in inches", "is 5x114.3 the same as 5x115", "will 6x135 wheels fit 6x139.7", or which vehicles use a pattern. Converts mm and inch notation, lists look-alike patterns that do not interchange, the vehicles in the dataset with that pattern, the lug tightening order and typical torque ranges by stud size (guidance only).
bolt_pattern_facts input schema
{
"type": "object",
"required": [
"pattern"
],
"properties": {
"pattern": {
"type": "string",
"description": "5x114.3, 5x4.5, 6x139.7, 8x6.5 …"
}
},
"additionalProperties": false
}bolt_pattern_facts output schema
{
"type": "object",
"required": [
"pattern_mm",
"pattern_in",
"lugs",
"lookalikes",
"vehicles_in_dataset",
"link",
"disclaimer"
],
"properties": {
"link": {
"type": "string"
},
"lugs": {
"type": "integer"
},
"pcd_in": {
"type": "number"
},
"pcd_mm": {
"type": "number"
},
"disclaimer": {
"type": "string"
},
"lookalikes": {
"type": "array",
"items": {
"type": "object",
"properties": {
"tier": {
"type": "string"
},
"gap_mm": {
"type": "number"
},
"pattern": {
"type": "string"
},
"interchangeable": {
"type": "boolean"
}
}
}
},
"pattern_in": {
"type": "string"
},
"pattern_mm": {
"type": "string"
},
"lug_sequence": {
"type": [
"array",
"null"
],
"items": {
"type": "integer"
}
},
"vehicles_in_dataset": {
"type": "array",
"items": {
"type": "object",
"properties": {
"link": {
"type": "string"
},
"make": {
"type": "string"
},
"model": {
"type": "string"
},
"years": {
"type": "string"
}
}
}
},
"typical_torque_by_stud": {
"type": "array",
"items": {
"type": "object",
"properties": {
"note": {
"type": "string"
},
"stud": {
"type": "string"
},
"lbft_max": {
"type": "number"
},
"lbft_min": {
"type": "number"
}
}
}
}
}
}bolt_pattern_facts annotations
{
"title": "Bolt pattern in mm and inches, look-alikes",
"readOnlyHint": true,
"openWorldHint": false,
"idempotentHint": true,
"destructiveHint": false
}Prompts
Not advertised
Resources
Not advertised
30-day availability
Aggregated from read-only remote checks; this is not a tool-execution or security guarantee.
- Successful checks
- 1 of 1 (100%)
- Average latency
- 422 ms
- 95th percentile latency
- 422 ms
Maintenance history
Public check and source-refresh events. Editorial and ownership records remain private.
- · probe · passed · 422 ms · metadata changed · 6 tool(s)
Connect from your client
Each snippet registers the same endpoint; pick the client you use.
Claude Code
Claude Code configuration
claude mcp add --transport http checkfitment-mcp https://checkfitment.com/mcp?src=mcpCodex
Codex configuration
codex mcp add checkfitment-mcp --url https://checkfitment.com/mcp?src=mcpCursor
Cursor configuration
{
"mcpServers": {
"checkfitment-mcp": {
"url": "https://checkfitment.com/mcp?src=mcp"
}
}
}Cline
Cline configuration
{
"mcpServers": {
"checkfitment-mcp": {
"type": "streamableHttp",
"url": "https://checkfitment.com/mcp?src=mcp",
"disabled": false
}
}
}VS Code
VS Code configuration
{
"servers": {
"checkfitment-mcp": {
"type": "http",
"url": "https://checkfitment.com/mcp?src=mcp"
}
}
}Gemini CLI
Gemini CLI configuration
gemini mcp add --transport http checkfitment-mcp https://checkfitment.com/mcp?src=mcpClaude Desktop
Claude Desktop configuration
{
"mcpServers": {
"checkfitment-mcp": {
"url": "https://checkfitment.com/mcp?src=mcp"
}
}
}Windsurf
Windsurf configuration
{
"mcpServers": {
"checkfitment-mcp": {
"serverUrl": "https://checkfitment.com/mcp?src=mcp"
}
}
}Let your agent find its tools
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