In short. An original (OEM) wheel is identified by the car maker's part number, cast or stamped on the inside of the wheel, usually on the back of the spokes or around the centre. Give that number to a dealer's parts department, or look it up in the maker's parts catalogue, and it leads to the models and production dates the wheel was fitted to. A "style number" (BMW) or a design name (Porsche, and in our reading most other makers) is a sales label for a look: in the BMW document we read, one style number covers two different sizes, and in a Porsche bulletin one design name covers three different front wheels. So identify by part number first, then check the size line beside it. A wheel with no car maker's part number is very likely not an original wheel, and its own markings tell you who made it.
Where the part number is, and what it looks like
Porsche says it plainly in a wheels and tyres bulletin for the 911 (992), dated 7 October 2025: "Identification on the inside of the wheel: wheel size, rim offset (RO) in mm, part number (without colour code marking FFF) and Porsche logo." In our reading, many original wheels follow that pattern: the size line, the offset, the car maker's part number and the maker's logo, close together, on the face you cannot see when the wheel is on the car.
Look on the back of the spokes, on the inner face of the barrel and around the centre bore. Clean the area first, then light it from the side: a cast number reads far better at a low angle than head on. A phone torch held flat against the barrel does the job.
If you need to take the wheel off to read it, lift the car with the jack and set it on axle stands before you put any part of your body under it; never rely on the jack alone. Refit the nuts or bolts to the car maker's torque, crosswise, and check them again after the first miles. Our guide to changing a wheel safely covers each step.
The number on the wheel can be shorter than the one on a parts invoice. Porsche's numbers in the bulletin take the form 992.601.025.FR, with a colour suffix (FFF) added for the finish, and the bulletin says the number inside the wheel is given without that colour code. Our reading: the same wheel can appear under a longer number on a parts invoice than on the casting, so compare the base number, not the whole string. We have not checked whether other makers work the same way.
The centre cap is not a clue you can rely on: it shows a logo rather than the wheel's part number, and it is easily swapped. Our guide to wheel centre caps explains how they fit.
Six identifiers, and what each one proves
Owners, sellers and forums use six different things to name a wheel. Only one of them pins down an exact wheel.
| Identifier | Where you read it | Example from a document we read | What it proves |
|---|---|---|---|
| Car maker's part number | Cast or stamped inside the wheel; parts catalogue; invoice | 992.601.025.FR (Porsche, front, 8.5J x 19, RO 52) | One wheel: size, offset, design and the cars it was released for |
| Style number or design name | Sales brochures, price lists, order papers; not always on the wheel | "Star Spoke style 427" (BMW i3); "Carrera 7" (Porsche) | A look. It can cover several sizes and offsets |
| Option code | The car's order, build sheet or price list | 2D6 and 2D7 (BMW i3, both style 427) | What the car was built with, if the wheels have not been changed since |
| Size line | Inside the wheel | 8.5J x 19, RO 52 | Width, flange, diameter and offset; not which car |
| Car's documents | Door-pillar placard (US, Canada); document of conformity (UK, EU); owner's handbook | Original tyre size; tyre/wheel combinations | What the car was built or sold with |
| Aftermarket permit or approval number | Outside or inside the wheel | "KBA 48207" (German permit) | A wheel that is not original, and the paper that lists its cars |
The last row matters for buyers. In our reading, a wheel sold as "OEM style" that carries a German KBA number or a UN approval mark with "124R", and no car maker's logo or part number, is not an original wheel, whatever it looks like. Do not judge by the wheel maker's name alone: original wheels are often made by a wheel firm for the car maker and can carry that firm's name beside the car maker's logo and part number. Our guide on how to read wheel markings explains those marks in detail.
BMW style numbers: a design, not a size
BMW gives each wheel design a style number, and its sales documents print it. The 2016 price guide for the BMW i3 from BMW of North America (effective 9 September 2015) lists the wheels like this: "Mega 19" BMW i Light Alloy Star Spoke wheels style 427", then the code and the sizes. The same style 427 appears twice: under code 2D6 with 19x5.0 wheels front and rear, and under code 2D7 (range extender) with 19x5.0 at the front and 19x5.5 at the rear. The guide also lists style 428 (2G5), style 429 (2G6) and the 20-inch style 430 (2T7), each with front and rear sizes.
Three things follow.
- A style number does not give you a size. Two cars on "style 427" can have different rear wheels. If you are buying one wheel to match, the part number or the size line decides, not the style.
- A style number is a key into the documents, not a stamp you can count on. We did not find an official BMW document that says where, or whether, the style number is marked on the wheel itself, and we do not claim it is. The reliable mark is the part number.
- Popular lookups such as "E46 wheel styles" are lists made by owners and sellers. We have not found a BMW source that publishes a complete list by chassis code, so we do not reproduce one. If you have the part number, the maker's catalogue gives the answer for your wheel without any list.
To go from your car to its style: find the option code on the build sheet or order papers, and match it in the price list for your model year, or ask a BMW parts department to read the car's build data from the VIN. To go from a wheel to its style: give the part number to the parts department.
Mercedes-Benz, Audi and other makers
In our reading, most other makers sell their designs under a name or a short description rather than a number, as Porsche does with "Carrera 7" or "Turbo S 4", and the name is again a sales label. The part number is what identifies the wheel. We have not found a public document from Mercedes-Benz or Audi that explains how their wheel part numbers are built, and the decodings that circulate come from clubs and sellers, so we do not repeat them. What works for every make is the same route: read the number on the wheel, then have it looked up in the maker's parts catalogue, either by a dealer's parts department or through the maker's own online parts or accessories shop where one exists for your country.
Bring the size line too. A parts adviser can check that the number and the size belong together; when they do not, you may be looking at a repaired, re-stamped or copied wheel.
Same design, different wheel: why the part number decides
Porsche's bulletin shows how much a design name can hide. We counted 12 design names (one, "OM-2", offered twice) and 42 distinct wheel part numbers for the 911 (992), without the colour suffix. Within that list:
- the "Carrera 7" design has two complete sets of part numbers for exactly the same sizes and offsets;
- the "Turbo S 4" design exists at the front as 9J x 20 RO 41, 8.5J x 20 RO 50 and 8.5J x 20 RO 40;
- and the bulletin states: "Only install wheels with identical part numbers on each axle."
Two 19-inch front wheels from the same bulletin show what a different offset does. Our calculation, with 1 inch = 25.4 mm, the outer flange at half the width minus the offset and the inner flange at half the width plus the offset, both measured from the face that bolts to the hub (the J width is taken between the flanges, so the flanges' own thickness is left out):
| Wheel (front, Porsche 911 992) | Width | Outer flange | Inner flange |
|---|---|---|---|
| "Carrera 7", 8.5J x 19, RO 52 | 215.9 mm | 107.95 − 52 = 55.95 mm | 107.95 + 52 = 159.95 mm |
| "992 Safari", 8J x 19, RO 38 | 203.2 mm | 101.6 − 38 = 63.6 mm | 101.6 + 38 = 139.6 mm |
| Difference | −12.7 mm | 7.65 mm further out | 20.35 mm closer to the hub face, so further from the suspension |
Both are genuine 19-inch Porsche front wheels for the 911 (992) range (the "992 Safari" is listed for the 911 Dakar), and they do not sit in the same place. That is why a seller's "19-inch original Porsche wheel" is not an identification. Our guide on wheel offset explains the arithmetic, and the wheel offset calculator runs it with your own figures. Onyx Forged does not recommend a size or an offset: the reference is the document your car maker publishes for your car.
From the car back to its original wheels
If you have the car but not the paperwork, these are the documents that say what it was built with.
United States. Federal standard FMVSS No. 110 requires a placard, normally on the driver's side B-pillar, that gives the "tire size designation ... for the tires installed at the time of the first purchase" (49 CFR 571.110, S4.3). It gives the original tyre size, not the wheel's part number, width or offset. The same standard requires rim markings, including the DOT symbol, only on rims for "vehicles other than passenger cars" (S4.4.2), so a passenger car wheel with no DOT stamp is not unusual.
Canada. Section 110 of the Motor Vehicle Safety Regulations applies Technical Standards Document No. 110 and requires the same placard information in both official languages, on one bilingual placard or on two.
United Kingdom and EU. A car sold with a European document of conformity has an entry 35, "Tyre/wheel combination", in the model set out in Annex VIII of Regulation (EU) 2020/683 (also published, as retained law, on legislation.gov.uk). The owner's handbook usually lists the wheel and tyre sizes too.
Australia. We could not reach the federal department's site that publishes the design rules on 16 October 2026, so we do not quote an Australian text. The owner's handbook and an authorised dealer's parts department remain the sources to use.
The VIN. In the United States, NHTSA's free decoder (vPIC) has 144 decoding variables, and only two concern the wheels: front and rear diameter in inches. Nothing on part number, style or offset; in two test decodes we ran, even those two fields came back empty. A dealer of the make can usually read much more from the same VIN, because the car's build data stays with the maker.
Once you have the original sizes, our page on bolt pattern and centre bore by make gives the hub figures that sources agree on. Original tyres can carry a maker's mark too (BMW's star, Mercedes-Benz MO, Porsche N): see OE tyre markings.
Original, identical, copy or aftermarket: what the rules say
UN Regulation No. 124, the text used in the UK and Europe to approve replacement wheels for cars, sorts wheels into families. It "does not apply to original equipment wheels or vehicle manufacturer's replacement wheels" (§ 1), so a genuine original wheel normally has no "E" mark and "124R" number, and that absence is not a warning sign.
| Family (Regulation No. 124) | What it is | What you will find on it |
|---|---|---|
| OE wheel (§ 2.3) | Fitted by the car maker in production | The car maker's logo and part number |
| Car maker's replacement wheel (§ 2.4.1) | Supplied by the car maker | The same |
| Identical replacement wheel (§ 2.4.2) | Same tooling and material as the car maker's wheel; differs "only by the absence of vehicle manufacturer's trademarks and part number" | A wheel maker's name and number, not the car maker's |
| Copy of the car maker's wheel (§ 2.4.3) | A copy made by a firm that is not the car maker's supplier, matching design, dimensions, inset and material | The wheel maker's markings, and an approval mark if it has one |
| Pattern part (§ 2.4.4) | Same inset, rim size, bolt pattern and spigot as the OE wheel; look and material may differ | The same |
| Special wheel (§ 2.5) | Anything else, for example another width or diameter | Outside Regulation No. 124; a national permit, such as a German KBA number |
For the wheels it covers, the regulation lists the markings: maker's name or trade mark, rim size, inset, date of manufacture ("at least the month and year") and "the wheel/rim part number" (§ 5.1.1 to 5.1.5). Here the part number is the wheel maker's, not the car maker's.
Germany's permits work the same way. In the KBA permit no. 48207 we read, the outside of the wheel carries "KBA 48207", and the inside carries the wheel type, trade mark, foundry mark, size, version code, bolt circle, offset, origin, month and year, and JWL. Japan's JWL standard asks for the JWL mark, the wheel size and offset, the name or trade mark of the car or wheel maker, and, for a wheel restricted to certain cars, "a symbol representing those vehicles", cast or stamped (MLIT, § 4.1, our translation).
If the wheel has no car maker's part number
Then it is very likely not an original wheel, even if the design looks familiar. Read what is there: the wheel maker's name, a permit or approval number, the date and the load. Those lead to the wheel maker's own documents, which list the cars it was made for. If there is nothing legible at all, you cannot check its load or its origin; ask the seller for the paperwork in writing, or walk away. Our used wheel buying checklist covers what to inspect next.
If you find a crack, a weld or a bend while reading the markings, do not refit the wheel: have it inspected before the car goes back on the road.
Frequently asked questions
Where is the part number on an OEM wheel?
On the inside: the back of the spokes, the inner barrel or around the centre bore, usually next to the size and offset. Porsche's bulletin lists exactly that set inside its wheels: size, offset, part number and logo.
How do I find my BMW wheel style number?
From the option code on the car's order or build sheet, matched against BMW's price list for that model year, or by giving the wheel's part number or the car's VIN to a BMW parts department. We found no BMW document saying the style number is marked on the wheel itself.
Does a style number tell me the wheel size?
No. In BMW's i3 price guide, style 427 is listed with 19x5.0 wheels all round under one code, and with a 19x5.5 rear under another.
Can I look up an OEM wheel by VIN?
Partly. NHTSA's free decoder only has front and rear diameter, and those fields were empty in our tests. A dealer of the make can usually read the car's build data from the VIN, which normally shows the wheels it was built with.
What if two wheels look the same but have different part numbers?
Treat them as different wheels until a parts catalogue says otherwise. Porsche lists the same design with different offsets, and asks for identical part numbers on each axle.
Why does my original wheel have no E124R or DOT mark?
UN Regulation No. 124 does not apply to original equipment wheels, and the US rim marking rule in FMVSS No. 110 covers rims for vehicles other than passenger cars. Neither absence is a fault.
Is a wheel with a KBA number original?
In our reading, no. A KBA number is a German permit issued for the wheel on its own (the permit we read calls such wheels "special wheels"); original wheels are covered by the approval of the car itself.
How do I tell a copy from an original?
Look for the car maker's logo and part number inside. A copy, under Regulation No. 124 (§ 2.4.3), is made by a firm that is not the car maker's supplier for that wheel and carries its own maker's markings.
Where to go next
For the size line and the norm marks, read how to read wheel markings; before paying for a used set, the used wheel checklist; before selling the originals, whether aftermarket wheels affect resale value. Onyx Forged is a French brand of made-to-order forged wheels, designed to JWL/VIA standards: see the catalogue.
Sources
- UN Regulation No. 124, replacement wheels for passenger cars: § 1, 2.3 to 2.5 and 5.1.
- Porsche AfterSales, bulletin 911 (992) 38/25, wheels and tyres (7 October 2025), published by NHTSA.
- BMW of North America, Pricing Guide i3 (i01), Model Year 2016 (effective 9 September 2015).
- Ministry of Land, Infrastructure, Transport and Tourism (Japan), technical standard for light-alloy disc wheels, § 4.1 (in Japanese).
- Kraftfahrt-Bundesamt, permit no. 48207 for an aftermarket wheel, § IV.2 (in German; copy published by a wheel retailer).
- 49 CFR § 571.110, FMVSS No. 110, S4.3 and S4.4.2.
- Canada, Motor Vehicle Safety Regulations, section 110.
- Regulation (EU) 2020/683, Annex VIII, entry 35.
- NHTSA, vPIC API, list of VIN decoding variables.
All pages were read on 16 October 2026.
The Onyx Forged design office.