BMW star, Mercedes MO, Porsche N: OE tyre markings

In short. No rule we read in the United Kingdom, the United States, Australia or Canada requires a tyre with a BMW star, a Mercedes-Benz MO, a Porsche N or an Audi AO. These marks say that a version of a tyre was developed or endorsed by one carmaker, sometimes for one model; the law looks at size, structure, load and speed ratings, and at the tyres on each axle matching in size and construction. Whether your car's maker expects a marked tyre, and which one, is in its handbook or with its dealer.

What each marking means

An OE (original equipment) marking is a short code moulded on the sidewall, usually near the size. Michelin explains it as a sign that your car's maker has chosen those tyres to be fitted as original equipment (our translation of its French page). Porsche's British page is the most direct: only N-marked tyres, it says, are checked and signed off by Porsche for "their performance, handling and safety characteristics".

The table sets each marking next to the source that defines it. Where the carmaker's own page answered, we used it; where it did not, we say so and give the tyre maker's wording instead.

How the Porsche code reads. Porsche's US page sets out the structure: "Following the N, a second letter indicates the model line and a number the tyre version." Its example is that a Macan tyre "will be marked NE0". The 0 is the first specific configuration, and higher numbers stand for later endorsed versions "of the tire with differing specifications". Older codes (N0 to N4, which Michelin lists) have no model-line letter.

The number is not a grade. Tesla's service manual puts it plainly: "a T1 Michelin Primacy is newer than a T0 Michelin Primacy, but is not necessarily newer than other models of T0 tires." The number counts versions of one tyre model; it does not rank tyres against each other. The same reading follows from Porsche's wording.

The letter says nothing about the tyre maker. One marking can appear on tyres from several manufacturers: the Tesla table we read lists T0 tyres from Hankook, Michelin, Goodyear and Pirelli for the 2024 Model 3.

What we could not check. BMW's and Mercedes-Benz's consumer tyre pages timed out when we tried them on 16 October 2026, and Audi's refused automated access. The MO, MOE, AO and AOE definitions therefore come from Continental, a tyre maker that produces tyres carrying them. BMW's press release dates from 2011 and announced a two-year warranty on star-marked tyres, starting in Germany on 1 September 2011; we do not know whether that warranty still runs, or in which countries.

Why a marked tyre is not the same as the plain version

A tyre with the same commercial name may exist in a marked and an unmarked version. Porsche says its tyres are "specifically developed for your Porsche model by leading manufacturers to our specifications", and describes each number as a version "with differing specifications". So the N version of a tyre is not necessarily identical to the one sold without a mark.

The tyre makers tie each mark to a behaviour. Continental writes that star-marked tyres are "custom-tailored to meet the specific safety and handling requirements of your BMW", with integration with xDrive and Dynamic Stability Control; that MO and MOE tyres are "fine-tuned to work seamlessly with your car's suspension and safety systems like ABS and ESP"; and that Audi tyres are tuned for the suspension and quattro systems. Michelin says carmaker-endorsed tyres are designed by its engineers "in close collaboration" with the carmaker (our translation).

What none of the sources we read publishes is a measured difference, on the road or on a test rig, between a marked tyre and the unmarked version of the same model. We cannot tell you how much longer an unmarked tyre takes to stop or how differently it steers. The carmakers state that it matters; they do not put a number on it in the pages we read.

Is a marked tyre a legal requirement?

Not in any text we read. Continental, a tyre maker, says so in its own words for four brands. It writes that you are not legally obliged to use tyres endorsed by Mercedes-Benz, or by Audi. For BMW, such tyres are "not always required, but it is highly recommended". For Tesla, endorsed tyres are "not strictly mandatory", though Continental adds that the tyres must "meet or exceed the load and speed ratings specified by Tesla". Michelin, for its part, recommends replacing tyres with tyres carrying the same OE marking. The law does not require; the carmakers and tyre makers advise.

What the law does check, country by country:

United Kingdom

The Road Vehicles (Construction and Use) Regulations 1986 say in regulation 26(1) that "pneumatic tyres of different types of structure shall not be fitted to the same axle of a wheeled vehicle". The "types of structure" are defined in regulation 26(6): diagonal-ply, bias-belted and radial-ply. The rule does not apply to a temporary-use spare on a passenger car driven at no more than 50 mph (regulation 26(5)). Nothing in regulations 24 or 26 mentions a carmaker's marking.

The MOT inspection manual (section 5.2.3, updated 14 October 2026) lists as major defects "Tyres on the same axle or on twin wheels are different sizes" (b) and "Tyres on the same axle of different structure" (c), and as major "A tyre load capacity or speed rating not in accordance with the minimum requirements" (a)(i). It does not list different brands, patterns or OE markings on one axle as a defect.

United States

At federal level, FMVSS No. 139 lists what must be moulded on the sidewall of a new light-vehicle radial tyre: the DOT symbol, the size designation, the maximum inflation pressure and load rating, the cord materials and ply count, "tubeless" or "tube type" and "radial". A carmaker's approval mark is not among them. FMVSS No. 110 requires the vehicle's placard to give the maker's recommended cold inflation pressures and the size of the original tyres, and sets the load on each tyre below the rating marked on its sidewall.

Periodic inspection, where it exists, is set by each state. Pennsylvania is the code we read: a car is rejected if "The tires used on the same axle are not the same size or type of construction—bias, belted, radial or snow" (67 Pa. Code § 175.80(e)(1)(x)), or if a tyre is "smaller than the manufacturer's recommended minimum size or below the manufacturer's recommended load rating" ((e)(1)(xxii)). Other states may differ.

Australia

The Australian Light Vehicle Standards Rules 2015 are a national model law, adopted by each state and territory; we read the version current at 22 November 2019. Rule 48 says a vehicle "must not have pneumatic tyres of different carcass construction fitted to the same axle", while allowing "different cord materials and a different number of plies". Rule 50 sets a minimum speed rating of 180 km/h for an ordinary car (140 km/h for a car with special off-road features), or the vehicle's top speed if lower. Rule 46 asks for tyres of sufficient size and capacity for the load on each axle. No rule mentions carmaker markings. Check the version in force where the car is registered: state transport sites refused us access.

Canada

Rules for a roadworthiness inspection are provincial. Ontario's Passenger / Light-Duty Vehicle Inspection Standard (section 9, item 3 a)) rejects a car when "nominal tire size is different between the left and right tires at the front or rear", when a "radial tire is mixed with non-radial anywhere on vehicle", and when a tyre "has a lower load rating / capacity than specified by the vehicle manufacturer". It notes that the maker's size and load requirements "can be located on the Tire Placard label". It says nothing about OE marks. We did not read the other provinces' standards.

Mixing marked and unmarked tyres

Three situations come up most often.

One tyre to replace on an axle. None of the four countries' texts asks for matching OE marks, but the UK MOT and the Pennsylvania and Ontario inspections check size, and all four check structure. Carmakers reason in pairs and sets: for the 19-inch Model 3 wheel, Tesla's service manual lists one tyre as "Recommended if you are not replacing the full-set of four tires" and another as "recommended when replacing all 4 tires". Tread depth, not only the mark, decides whether the new tyre matches the old one.

Two versions of one mark on an axle (N0 and N1, for example). Porsche says the numbers are versions with differing specifications. We read no Porsche text that allows or forbids pairing them on one axle, and no law goes down to that level. That is a question for the brand's service department.

All-wheel-drive cars. This is where a difference between tyres matters most, because the driveline links the axles. Continental ties the star marking to xDrive and the AO marking to quattro. We found no tolerance, published by BMW, Audi or Mercedes-Benz in the pages we read, for the circumference difference their all-wheel-drive systems accept. The handbook of your car is where that figure lives, if the maker gives one. Whether to replace two tyres or four on an all-wheel-drive car is covered in our guide to new tyres on the front or the back.

Our calculation: what wear does to two tyres on one axle

To put the question in proportion, we calculated what a difference in tread depth does to two tyres of the same size. A tyre with d mm less tread has a diameter 2 × d mm smaller, so a circumference π × 2 × d mm shorter, and it turns more times per mile.

Theoretical diameter: rim diameter in millimetres plus two sidewall heights (width × aspect ratio). These are unladen figures; under load the rolling radius is smaller and the real difference can vary. The two sizes serve the arithmetic and belong to no car named in this guide.

What the calculation shows: a few millimetres of wear change a tyre's circumference by around one per cent. We do not know the circumference difference between a marked tyre and its unmarked version, because no source we read publishes it, so we cannot compare the two. To compare two sizes, our tyre size calculator works out the diameters; our guide to tyre rotation explains how rotation keeps wear even.

How to read the marking on your sidewall

Our guide to reading a tyre covers the full sidewall. For the OE question, in order:

1. Read the size, load index and speed rating of the tyre on the car and compare them with the placard (door pillar or fuel flap) or the handbook. These are what an MOT tester or an inspector checks.
2. Find the legal approval. In the US, the DOT symbol and tyre identification number; in the UK and Europe, an "E" or "e" approval mark. The MOT manual asks testers to accept a tyre marked "Not for Highway Use" only if it carries an E mark.
3. Look for an OE mark next to the size: a star, MO, MOE, MO1, N with a number or a letter and a number, AO, AOE, RO1, T0 and so on. A tyre may carry none and still be fully legal.
4. Note whether the tyre is a run-flat. The "Extended" versions (MOE, AOE) are named separately by Continental, but the pages we read do not say what "Extended" covers. A run-flat tyre is built differently from a conventional one, so ask your fitter before mixing the two on one axle.
5. Check the carmaker's list. The handbook or a dealer says which mark the maker expects for your model and your size.

Pressures are those of the carmaker, on the placard; our tyre pressure guide explains where to find them. If a tyre shows damage, a bulge or exposed cord, have it checked before you drive on.

And after a change of wheels?

An OE marking belongs to a tyre in a size the carmaker has listed. A size the carmaker did not list has, by definition, no marked tyre for it; the question then becomes the size itself, its load and speed ratings, and whether it fits, which our guide to what size wheels fit your car covers. For a Tesla, our Model 3 and Model Y wheel guide gathers the sizes Tesla publishes. Onyx Forged does not recommend a size or an offset: the reference stays the carmaker's documentation.

Frequently asked questions

Do I have to fit star-marked tyres on a BMW?

No rule we read in the UK, the US, Australia or Canada requires them. Continental writes that BMW-endorsed tyres are "not always required, but it is highly recommended". Your BMW's handbook or dealer says what BMW expects for your model.

What does N0 mean on a Porsche tyre?

N means endorsed by Porsche, and the number counts endorsed versions of that tyre: 0 is the first, higher numbers are later versions with differing specifications. Newer codes add a model-line letter, for example NE0 for the Macan.

What do MO, MOE and MO1 mean?

MO is "Mercedes Original" and MOE "Mercedes Original Extended", according to Continental; Michelin lists MO1 for AMG. Mercedes-Benz's own pages did not respond when we tried them.

What do AO, AOE and RO1 mean on an Audi tyre?

AO is "Audi Original" and AOE "Audi Original Extended", according to Continental; Michelin lists RO1 for quattro. Continental adds that you are not legally required to use Audi-endorsed tyres.

Is T0 better than T1 on a Tesla?

Neither is a grade. Tesla's service manual says a T1 is a newer version than the T0 of the same tyre model, but not necessarily newer than other T0 tyres, and that this information applies only to North America.

Can I put a marked and an unmarked tyre on the same axle?

The texts we read check size and construction on an axle, not OE marks. The carmakers and tyre makers still advise matching marks, and on an all-wheel-drive car the tread depth matters too: ask the brand's service department.

Will an unmarked tyre fail the MOT or a state inspection?

Not on the mark alone, in the texts we read. The MOT manual checks size and structure on each axle, load capacity and speed rating; Pennsylvania and Ontario check size, construction and load rating. None of them looks for a star or an MO.

Does an OE mark affect my warranty?

BMW's 2011 press release tied a two-year tyre warranty to manufacturer-endorsed tyres, starting in Germany; we do not know whether it still applies. For any current warranty, read the terms of the carmaker or the tyre maker concerned.

Made-to-order wheels and OE tyres

At Onyx Forged, the design office sets out in writing the dimensions of each set of wheels before production, and the choice of tyre stays with what the car maker's documentation lists. Our wheels are designed to JWL/VIA standards. To build a set, see how to customise a set.

Sources

• Porsche, Tires (USA) and Tyres (UK).
• BMW Group PressClub, New free BMW and MINI tyre warranty, 16 August 2011.
• Tesla, Model 3 (2024+) service manual, Replacement Tire Information.
• Continental Australia, tyres for BMW, Mercedes-Benz, Audi and Tesla.
• Michelin (in French), Help me choose the right tyre and Original equipment tyres; translations ours.
• The Road Vehicles (Construction and Use) Regulations 1986, regulation 24 and regulation 26.
• GOV.UK, MOT inspection manual, section 5.2.3 Tyres, updated 14 October 2026.
• 49 CFR § 571.139, FMVSS No. 139 and 49 CFR § 571.110, FMVSS No. 110 (Legal Information Institute, Cornell).
• 67 Pa. Code § 175.80, Inspection procedure (Pennsylvania).
• Parliamentary Counsel's Committee, Australian Light Vehicle Standards Rules 2015, current as at 22 November 2019.
• Ontario Ministry of Transportation, Passenger / Light-Duty Vehicle Inspection Standard, section 9.

All pages were read on 16 October 2026.

The Onyx Forged design office.