VW Parts Glossary: Every Term You Need to Know

Aftermarket

Everything made by a third party rather than VW's original supply chain. It's a much wider category than people assume, stretching from established performance brands with decades of motorsport pedigree to no-name suppliers worth avoiding entirely. The brand behind an aftermarket part matters more than the word itself.

Genuine VW parts

Components sold directly through Volkswagen's own network, boxed with the VW badge. They're made to exact factory spec, and the price reflects that badge and the dealer markup that comes with it. Our genuine VAG parts range covers exactly this category.

OE part number

The unique reference code stamped on a component or printed on its packaging. Quote this number when ordering and you remove almost all the guesswork around whether a part will actually fit.

OEM

Stands for Original Equipment Manufacturer. An OEM part is made by the same factory that supplied the component originally, just sold without the VW packaging or the dealer price tag. Often it's physically identical to the genuine part.

VIN

Stands for Vehicle Identification Number, sometimes called the chassis number. It's the most precise way to confirm exact specification, since model years and trim levels can share a name while running completely different parts underneath.

VW genuine parts catalogue

The official listing of parts and part numbers Volkswagen maintains for each model. Cross referencing your old component's part number against this catalogue is the most reliable way to confirm fitment, far more reliable than trusting a product photo.

Catback exhaust

Covers everything from the catalytic converter backwards, the section most people mean when they talk about an aftermarket exhaust system. A Milltek catback is a common starting point on most VAG platforms.

Decat

Means removing the catalytic converter from the exhaust system, usually replaced with a straight pipe or sports cat to improve exhaust flow. It's worth knowing this isn't road legal in the UK and will fail an MOT, as well as the fact that Stage 2 software is usually required when fitting a downpipe upgrade.

Diverter valve (DV)

Releases pressure from the turbo system during gear changes or when lifting off the throttle. A failing standard diverter valve is a common cause of boost leaks and is often one of the first parts upgraded on a tuned car.

Downpipe

The section of exhaust running from the turbo to the rest of the system, often the first upgrade in a performance exhaust setup since it sits closest to where restrictions cause the most harm.

Intercooler

Cools compressed air from the turbo before it reaches the engine, since cooler air is denser and supports more power. Upgraded intercoolers like those from Forge are common on tuned cars running more boost than standard.

Stage 1, 2 and 3

Describe how far a tuning package goes. Stage 1 is software only, no hardware changes required. Stage 2 adds supporting hardware like an upgraded intercooler or downpipe to handle more power safely. Stage 3 usually means a turbo upgrade and significant supporting modifications.

Anti-roll bar (ARB, sometimes referred to as Sway Bars)

Connects the suspension on each side of an axle, reducing body roll through corners. Stiffer aftermarket bars from brands like 034Motorsport sharpen handling without the full cost of a coilover setup.

Bushes

The rubber or polyurethane components that cushion suspension joints. Worn bushes cause vague, clunky handling, and upgrading to stiffer polyurethane versions is a popular way to sharpen response.

Camber

The angle of the wheel when viewed from the front of the car, measured as negative when the top of the wheel leans inward. On a lot of cars, lowering increases negative camber as a side effect, but on modern VWs that's not always the case. We often need to fit upgraded suspension arms or camber top mounts to introduce the camber ourselves, rather than relying on the drop alone to do it.

Coilovers

Combine the spring and damper into one adjustable unit, usually allowing height and sometimes damping to be set to your preference. They're a step up from fixed lowering springs in terms of flexibility and cost.

Drop links

Connect the anti-roll bar to the suspension and often need replacing or adjusting when a car is lowered, since standard length links can bind or wear prematurely once ride height changes.

Haldex

The system used on many 4Motion and some Quattro models to manage power distribution to the rear axle. Like DSG, it has its own service requirements separate from a standard service, which our Haldex servicing covers. Some Haldex systems can also be tuned, and our APR Stage 2 AWD Controller Software for Gen 5 Haldex is a good example, sharpening AWD response and letting drivers switch between full AWD and FWD modes on the fly.

LSD

Stands for limited slip differential, a unit that helps put power down more effectively by limiting how much one wheel can spin relative to the other under load. A Wavetrac or Quaife differential is a common upgrade on front-wheel-drive VAG cars that struggle with wheelspin under power.

Big brake kit

Upgrades the standard calipers and discs to larger components, usually to improve stopping power and resist fade under repeated hard use. These are popular on cars that have had a remap, since more power needs more braking capability to match.

Block exemption

Refers to the rules allowing independent garages to service and repair your car without affecting your manufacturer warranty, provided the work follows the official schedule and uses parts of the required spec. It ended the old assumption that only a main dealer could touch a car under warranty.

Brake pad compound

Refers to the friction material used in a pad, which affects how it performs cold, how much dust it produces and how it behaves at higher temperatures. EBC and VBT offer compounds ranging from quiet daily options to track-focused pads that need heat to work properly.

MOT

The UK's annual roadworthiness test, required once a vehicle turns three years old. Several performance modifications, decat pipes included, will cause an MOT failure if not reverted or fitted with road legal alternatives.