Compatibility database for tyres & wheels by vehicle
A structured catalogue of tyre and wheel sizes by vehicle modification. For every modification the database returns the factory (is_stock=true) and tuning tyre and wheel sizes, drilling parameters (PCD, DIA, ET, bolt_count/drilling) and bolt size, each tagged with its axle (front / rear / universal).
- Full SQL dump or REST API access
- Factory (is_stock=true) and tuning tyre and wheel sizes
- Staggered setups (axle: front / rear)
Try the picker against this database
Pick a vehicle below to see the exact data structure returned by the database.
Show API JSON response
What the API actually returns
A /v1/tires/modifications/{id} call returns one JSON object with a car block (brand, model, year, modification name), wheel_specs with drilling parameters, and two size lists — for tyres and wheels — each split into factory and tuning groups.
{
"id": 501,
"car": {
"brand": { "id": 1, "name": "Audi" },
"model": { "id": 12, "name": "A4 B8" },
"year": 2012,
"modification": "2.0 TDI"
},
"wheel_specs": {
"pcd": 112,
"bolt_count": 5,
"drilling": "5x112",
"dia": 57.1,
"bolt_size": "M14x1.5"
},
"tires": {
"factory": [
{ "width": 225, "height": 50, "diameter": 17, "size": "225/50 R17", "is_stock": true, "axle_title": "Універсальна" }
],
"tuning": [ … ]
},
"wheels": {
"factory": [
{ "width": 7.5, "diameter": 17, "et": 45, "size": "7.5x17 ET45", "drilling": "5x112", "is_stock": true }
],
"tuning": [ … ]
}
}
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Get instant access to the API keys or download the full database dump file.
Wheel, Rim & Tyre Specifications: Complete Technical Guide
Safe wheel fitment requires strict adherence to hub geometry, brake clearance, and automaker load limits. Below is an in-depth engineering breakdown of PCD, ET, DIA, tire pressure, and proper OEM vs tuning fitment guidelines.
Wheel Rim Specifications (PCD, Offset ET, Center Bore DIA, Rim Width, Fasteners)
Geometric wheel-to-hub mounting parameters and allowable engineering tolerances
| Parameter | Designation | Unit | Definition & Measurement | Safety & Operational Impact |
|---|---|---|---|---|
| PCD PCD (Pitch Circle Diameter / Bolt Pattern) | 5x112, 5x114.3, 4x100 | lugs × mm | Number of lug holes and diameter of the circular centerline they lie on. On a 4-lug wheel PCD is measured directly between centers of opposing holes; on a 5-lug wheel, distance between adjacent hole centers is multiplied by 1.7012. | Strictly forbidden to mount wheels with different PCD (e.g. 5x110 onto 5x112). Even a 1–2 mm difference leads to crooked bolts, uneven torque, severe vibration, and sheared wheel studs at highway speeds. |
| ET ET (Einpresstiefe / Wheel Offset) | ET45, ET35, ET-15 | mm | Distance in millimeters from the wheel hub mounting surface to its true centerline plane. Can be positive (ET > 0, wheel tucked into fender), zero (ET = 0), or negative (ET < 0, wheel poking outward). | Directly determines Scrub Radius and wheel bearing load. Lower ET pushes the wheel out and stresses suspension bushings; higher ET pulls the wheel inward, risking rub against suspension struts or brake calipers. Safe variance is within ±5 mm of OEM. |
| DIA / CB DIA / CB (Center Bore / Hub Diameter) | 57.1, 66.6, 72.6, 67.1 | mm | Diameter of the center hole in the wheel that matches the vehicle hub collar. Provides primary high-precision wheel centering relative to the rotational axis before lug torquing. | If wheel DIA is larger than vehicle hub, hub-centric rings (aluminum or polycarbonate) are mandatory. Without them, progressive 80–120 km/h steering vibration occurs. If wheel DIA is smaller than hub, mounting is physically impossible. |
| Rim Width & J Contour (Flange Shape) (Rim Width / H2) | 6.5J, 7.5J, 8.0J, 9.5J | inches (") | Distance between inner tire-bead retaining flanges of the rim. Letter J specifies passenger car flange contour and profile height. H2 indicates double hump ridges locking tubeless tire beads during heavy lateral cornering. | Dictates compatible tire section width range. Engineering rule: tire section width must be 20–30% wider than rim width. Excessively narrow rims pinch sidewalls; excessively wide rims stretch tires, eliminating curb protection. |
| Fasteners (Lug Bolts / Nuts & Seat Chamfer) (Wheel Fasteners) | M14x1.5, M12x1.25 | thread / seat | Fastener hardware (lug bolt or pressed wheel stud with nut), thread size and pitch (e.g. M14x1.5, M14x1.25, M12x1.5). Seat profile: 60° conical/taper, spherical/radius (R12–R14 ball seat), or flat washer seat. | Seat profile matching is critical: using conical bolts in spherical holes creates point contact, self-loosening under vibration, and severe lug seat deformation. |
Tyre Specifications (Size Markings, Load/Speed Ratings, Inflation Pressure)
Decoding tyre sizing, load/speed ratings, and axle-specific inflation standards
| Parameter | Example | Unit | Physical Meaning | Handling & Vehicle Dynamics |
|---|---|---|---|---|
| Section Width (Section Width) | 205, 225, 255 | mm | Linear distance between outer sidewalls of an inflated tire under nominal pressure, excluding protective ribs, bar-codes, and embossed lettering. | Wider profile increases contact patch area and dry lateral grip, but slightly increases rolling resistance (2–4% higher fuel consumption) and raises hydroplaning risk on standing water. |
| Aspect Ratio (Sidewall Height Series) (Aspect Ratio) | 45, 50, 55, 65 | % of width | Ratio of sidewall section height to nominal section width expressed as percentage. For 225/45, sidewall height is 225 × 0.45 = 101.25 mm. | Low profile (≤50%) provides minimal sidewall flex and lightning-fast steering response; high profile (≥60%) absorbs rough potholes and protects alloy rims from impact cracks. |
| Casing Construction R (Radial Cord) (Radial / R) | R (Radial) | cord type | Casing cord plies run radially at 90° to the rolling direction from bead to bead. Letter R stands for Radial, never "radius". | Radial ply layout minimizes internal heat buildup at highway speeds, stabilizes contact patch geometry, and doubles tread life compared to historic bias-ply tires. |
| Load Index & Speed Rating (Load & Speed) | 91V, 94W, 98Y, 103W | code (kg / km/h) | Numerical load index (91 = 615 kg, 94 = 670 kg, 98 = 750 kg, 103 = 875 kg) and alphabetical speed rating (H = 210 km/h, V = 240, W = 270, Y = 300 km/h). | Strict safety mandate: never install tires with a load index lower than OEM manufacturer specification. For heavier SUVs and EVs, XL (Extra Load / Reinforced) construction is mandatory. |
| Cold Tire Pressure (Comfort vs Loaded) (Pressure) | 2.2 / 2.4 Bar (32/35 PSI) | Bar / PSI / kPa | Inflation pressure inside cold tire cavity measured before driving. Specified on driver B-pillar placard broken down by axle and payload (partial vs full load). | Under-inflation by 0.4–0.5 Bar causes severe sidewall overheating (blowout hazard), shoulder wear, and 3–5% fuel penalty. Over-inflation crowns tread center and reduces traction. |
Factory OEM vs Tuning (Plus Sizing) & Staggered Setups
The Fitment API categorizes dimensions into factory (is_stock=true) original equipment, and tuning certified alternatives. Plus sizing allows installing larger rim diameters while decreasing aspect ratio to keep overall tire diameter within ±2% (ETRTO standard). For sports and performance vehicles, the database provides staggered fitments with separate front and rear axle specs, preventing transfer case damage on AWD vehicles.
Factory Stock Sizes
Engineered by automakers for curb weight, ride height, suspension kinematics, and brake clearance. Delivers optimal balance between comfort, fuel economy, and component lifespan.
Alternative Sizes
Upgrading to larger diameter rims (Plus 1 / Plus 2: e.g. R16 to R17 or R18) with lower aspect ratio tires. Rolling diameter must stay within -2%...+1.5% for accurate speedometer and ABS/ESP operation.
Performance Staggered Wheels
Wider rear rims and tires to maximize traction under high torque. On AWD vehicles (xDrive, 4MATIC, quattro), front and rear rolling circumference must match within 1% to protect the transfer case.
Tyre Comparison & Wheel Offset (ET) Calculator
Compare tire and wheel dimensions in real time. Calculate ground clearance changes, speedometer discrepancy, inner suspension clearance, and outer fender extension.
Excellent size match. Overall diameter variance is within ±2%, ensuring correct ABS, ESP, and transmission sensor calibration.
Note: when extending wheels outward by more than 15 mm, check fender lip clearance at full suspension travel.
Database Query Structure Demo
Example real dataset returned for vehicle modifications by Fitment API
Frequently Asked Questions About Tyre & Wheel Fitment
Authoritative engineering answers optimized for Google Search and AI Overviews
How do you decode tyre sidewall markings (e.g. 205/55 R16 91V)?
A tyre marked 205/55 R16 91V breaks down as follows: 205 is nominal section width in millimeters; 55 is aspect ratio (sidewall height is 55% of 205 mm = 112.75 mm); R indicates Radial cord construction (not radius); 16 is wheel rim diameter in inches; 91 is load index (up to 615 kg per tyre); V is speed rating (maximum sustained speed of 240 km/h).
What is wheel PCD (bolt pattern) and can you install wheels with a different PCD?
PCD (Pitch Circle Diameter) is the number of bolt holes and the diameter of the circular centerline they lie on (e.g., 5x112: 5 lugs on a 112 mm circle). Installing wheels with a different PCD (such as 5x110 instead of 5x112) is strongly prohibited without certified adapters: bolts screw in crookedly, resulting in uneven clamping force, severe high-speed vibration, and extreme risk of sheared studs.
What is wheel offset (ET) and how does it affect vehicle handling and suspension?
Wheel offset (ET, Einpresstiefe) is the millimeter distance from the wheel hub mounting face to its centerline. Lower or negative offset pushes wheels outward toward the fender; higher positive offset tucks wheels inward. Changing offset alters Scrub Radius, increasing steering kickback, wheel bearing wear, and risk of rubbing against shock absorbers or brake calipers. Safe variance is generally within ±5 mm of OEM.
What does DIA (center bore) mean and when are hub-centric rings required?
DIA (Center Bore) is the machined hole in the center of the wheel that matches the vehicle hub lip (e.g. 57.1 mm for VW, 66.6 mm for Mercedes). It centers the wheel prior to lug tightening. If wheel DIA is larger than the hub, hub-centric rings are mandatory to prevent severe 80–120 km/h steering vibration. If wheel DIA is smaller than the hub, the wheel will not fit.
What is the difference between factory OEM and tuning wheel sizes?
Factory OEM sizes are engineered and certified by the automaker for optimal safety, suspension geometry, and fuel economy. Tuning sizes (Plus Sizing) use larger rims with lower-profile tyres while maintaining total rolling diameter. Diameter variance must stay within -2% to +1.5% (ETRTO standard) to ensure accurate speedometer reading and proper ABS/ESP calibration.
What are staggered wheels and can they be fitted on all-wheel-drive (AWD) cars?
Staggered fitments have wider rear wheels and tyres than front (e.g. 245/40 R19 front, 275/35 R19 rear), common on rear-wheel-drive performance cars. On AWD vehicles (BMW xDrive, Mercedes 4MATIC, Audi quattro), staggered setups are permissible ONLY when front and rear rolling circumferences match within 1%, preventing permanent strain and overheating of the center transfer case.
What is the correct tyre pressure and how does it vary by axle and load?
Optimal pressure is specified on the driver door jamb placard or fuel filler door and should be checked when tyres are cold. Normal passenger car pressure ranges from 2.1 to 2.5 Bar (30–36 PSI). Front and rear axles often differ, and rear pressure should be increased by +0.3–0.5 Bar when carrying full cargo or passengers. Under-inflation increases fuel consumption by 3–5% and overheats sidewalls; over-inflation causes premature center wear and reduces wet grip.
How does vehicle fitment lookup work via Fitment API?
Fitment API provides cloud REST API endpoints and SQL dumps. When queried by make, model, year, and engine modification, it returns exact drilling specs (PCD, DIA, ET, fasteners), recommended tire pressures, and full lists of factory OEM and tuning dimensions categorized by axle (front, rear, universal), enabling turnkey vehicle lookup for auto parts and tyre stores.