Genuine, OEM, Pattern and Aftermarket Parts Explained
Four words, used more or less interchangeably by people selling you things, and they do not mean the same thing. The difference between them is often the difference between paying £90 and paying £25 for what comes out of the same factory.
I am a time served maintenance engineer and a biker rather than a parts dealer, so I have no stake in talking you into the expensive box or the cheap one. Here is what the four terms actually mean and where the money goes.
What the four words mean
| Term | What it actually is | Who made it |
|---|---|---|
| Genuine | Supplied in the motorcycle manufacturer’s own packaging, with their part number on it | Usually a specialist subcontractor, not the bike factory |
| OEM | Made by the company that supplied the original part, sold in that company’s own box | The same subcontractor, minus the badge and the markup |
| Pattern | A copy of the original, made by somebody else to fit the same application | A third-party manufacturer, quality anywhere from excellent to dreadful |
| Aftermarket | A part designed as an alternative, sometimes an upgrade rather than a copy | A third party, often specialising in that one component |
The one that surprises people is the first row. Motorcycle manufacturers do not make bearings, or spark plugs, or brake pads, or chains. They buy them from firms that make nothing else, and then put their own box round them.
Why the same part costs three different prices
A wheel bearing is a good example, because bearings are made by bearing companies and nobody pretends otherwise.
- The genuine part comes in the manufacturer’s box with the manufacturer’s number. It carries the cost of their distribution network, their warranty exposure and their brand.
- The OEM part is the identical bearing in the bearing maker’s own box. Same factory, same specification, frequently half the price.
- The pattern part is a bearing of the same dimensions from somebody else, which may be to the same standard or may not.
The trick worth knowing: take the part out and read what is stamped on it. Bearings, seals, plugs, chains and electrical components almost always carry the actual maker’s name and their own reference. Search that reference instead of the motorcycle manufacturer’s number and the price often falls off a cliff for exactly the same item.
Where I fit pattern parts and where I do not
This is the part people want a rule for, and there is not one rule. There is a rule per category.
| Component | What I fit | Why |
|---|---|---|
| Brake pads and discs | Genuine or a known brand | Braking is not the place to save £15. Unbranded pads can glaze, fade or eat discs. |
| Wheel and steering bearings | OEM in the bearing maker’s box | Same item, better price. Buy on the bearing reference, not the bike part number. |
| Filters | Genuine or a reputable pattern brand | Cheap oil filters can have poor bypass valves. Not worth the gamble on an engine. |
| Bodywork and cosmetics | Pattern or used genuine, happily | If it fits and looks right, it has done its job. Check the fixing points. |
| Levers, mirrors, footpegs | Pattern | Simple parts, easy to judge by eye, and a failure is an inconvenience not a crash. |
| Electrical and engine management | Genuine or used genuine | Pattern regulators and sensors are the single most common source of intermittent faults I hear about. |
| Chains and sprockets | Known aftermarket brand | The specialists here are often better than the original fitment. This is where aftermarket genuinely beats genuine. |
How to tell what you are actually being sold
Listing language is deliberately slippery. These are the tells.
- “Genuine quality” and “OEM style” mean pattern. If it were genuine, the listing would say genuine and show the box.
- “Fits” is not “is”. A part that fits your bike is not necessarily the part specified for your bike.
- A photograph of a box tells you more than any description. No box in the pictures usually means no box.
- Check the part number in the listing against the diagram. Genuine parts are sold against the manufacturer’s number. Pattern parts are sold against a model name.
- Price is information. A genuine part at a third of the going rate is not a bargain, it is a different part or a fake.
The counterfeit problem
This is separate from pattern parts and it is worth keeping separate in your head. A pattern part is an honest copy sold as a copy. A counterfeit is a copy sold as the original, in a fake box, at nearly the original price.
- Brake components, chains and bearings are the common targets because they are consumable, expensive and hard to judge by eye.
- Packaging is getting harder to call. Holograms and part-number stickers are copied too.
- Buy where there is recourse. Established sellers with a returns policy and a marketplace protection scheme behind them are worth the extra few pounds.
- A counterfeit is worse than a pattern part, because with a pattern part you at least know what you have bought and can judge it accordingly.
Does any of this affect your MOT or insurance
I am not a lawyer or a broker, so take this as a pointer to check rather than as advice.
- The MOT tests condition and function, not provenance. A pattern brake disc in good order passes. A genuine one worn past its limit does not.
- Like-for-like replacement is normally not a modification. Fitting a replacement part of the same specification is maintenance.
- Changing what the bike does is a modification. Exhausts, suspension, and anything affecting performance or noise usually need declaring. Check your policy wording rather than assuming.
- Keep the receipts for safety-critical parts. If something is ever questioned, being able to show what you fitted and when is worth having.
Common questions
Is OEM the same as genuine?
Not quite. Both come from the firm that made the original component. Genuine comes in the bike manufacturer’s box with their number and their markup. OEM comes in the component maker’s own box.
Are pattern parts always worse?
No. For chains, sprockets, brake lines and suspension, specialist aftermarket firms often produce something better than the original fitment. For sensors and regulators, pattern parts have a poor reputation and it is deserved.
How do I find the OEM reference?
Take the old part off and read it. Bearings, seals and electrical components carry the actual manufacturer’s marking. That reference is what you search.
Why is the genuine part so expensive?
Distribution, warranty and low volume. A part that sells a few hundred units a year worldwide carries a share of the cost of keeping a parts operation running for a bike that left the showroom fifteen years ago.
What about used genuine parts?
Often the best answer of the lot for anything that does not wear. A used genuine bracket, panel or casting is the correct part at pattern-part money.
Where this site fits
The parts search on this site runs an eBay search filtered to motorcycle parts and set to sellers worldwide. Paste in a manufacturer part number and you will see genuine, OEM and pattern options side by side, which is the quickest way to see the spread for yourself.
Before you search, it helps to have the right part number rather than a model name. If the part has gone extinct in this country, buying from Japan is often the answer for a Japanese machine.
If you buy something after searching here I earn a small commission from eBay. It costs you nothing extra and it does not change what you are shown.