Short answer: a spacer moves a wheel outward but keeps the same stud pattern. A PCD adapter moves the wheel outward and changes the stud pattern, so you can fit a wheel that would otherwise never bolt up. If you have found a set of wheels you love and they are the wrong pattern, an adapter is how people solve it.
PCD stands for pitch circle diameter — the diameter of the imaginary circle running through the centre of your wheel bolts. 5x112 means five bolts on a 112mm circle.
Adapter or spacer — which do I need?
| Spacer | PCD adapter | |
|---|---|---|
| Stud pattern | Unchanged | Changed |
| Typical thickness | 10–25mm | 20mm and up |
| Fixing | Slip-on (longer bolts) or bolt-on | Always bolt-on — its own studs |
| Used for | Filling the arch, caliper clearance | Fitting wheels from a different car |
An adapter is always thicker than a plain spacer, because it has to carry two separate sets of fasteners without them fouling each other. That thickness is not optional, and it is the first thing to plan around.
The conversions people actually ask for
5x100 to 5x112 — older VW and Audi to newer wheels
VW and Audi used 5x100 on the Mk4 Golf, early A3, Polo, Ibiza and Octavia, then moved to 5x112. That leaves a lot of good 5x112 wheels that will not fit a 5x100 car. This adapter solves it, and it is probably the single most common conversion we sell.
25mm PCD adapters — 5x100 to 5x112 — £102.84 a pair
5x112 to 5x130 — Audi to Porsche
Porsche has used 5x130 across the 911, Boxster, Cayman and Cayenne for decades. Audi uses 5x112 on most of the range. If you want a set of Porsche wheels on an Audi, this is the adapter that does it.
25mm PCD adapters — Audi 5x112 to Porsche 5x130 — £102.84 a pair
5x108 to 5x112 — Ford to Audi
Ford's 5x108 is close enough to 5x112 to tempt people into forcing it. Do not. A 4mm difference across the pitch circle means the bolts load the wheel unevenly and you will eventually crack something. Use the adapter.
25mm PCD adapters — Ford 5x108 to Audi 5x112 — £102.84 a pair
5x130 on the Q7 and Cayenne
The Audi Q7 4L and the Porsche Cayenne share 5x130, so these are spacers rather than adapters — but the same sizing rules apply.
- 25mm spacers — Audi Q7 4L 2005–2015
- 30mm spacers — Porsche 911, Boxster, Cayman, Cayenne and Audi Q7
Four things to check before you buy
1. Track width — the one people forget
A 25mm adapter pushes each wheel out 25mm. That is 50mm added across the axle. On a car that already fills its arches, that tyre is coming out past the bodywork, which looks wrong and causes problems at roadside and with your insurer.
Before ordering, work out what offset the donor wheels are. A Porsche wheel with a lower offset on a 25mm adapter can push out a very long way. Sometimes the right answer is a different wheel rather than a different adapter.
2. Centre bore, on both faces
An adapter has two bores to get right: the inner one that locates on your car's hub, and the outer one the new wheel locates on. Both must be correct or the wheel is centred by its bolts, which is how you end up with a vibration that balancing will never cure.
Every adapter we sell is hub-centric on both faces and machined for the specific pairing in the listing.
3. Bolt or stud thread
The two cars may use different threads. Audi commonly uses M14x1.5, Porsche M14x1.5, Ford M12x1.5, newer BMW M14x1.25. The adapter handles the change — it bolts to your hub with your thread and presents studs in the donor wheel's thread. Check the listing states both.
4. Load rating
An adapter carries the full corner weight of the car plus everything that happens over a pothole. Buy a forged aluminium adapter from a known manufacturer with a stated load rating. This is not a part to buy on price alone — it is the only thing holding your wheel to your car.
Are PCD adapters legal in the UK and Ireland?
They are not illegal to fit to a road car. The practical considerations are the same as for spacers: the tyre must stay within the body line on applicable vehicle categories, and you must declare the modification to your insurer. Failing to declare is what causes problems, not the part itself. There is no specific MOT test for adapters, but a tester will check for secure fixings, bearing play and tyre fouling.
We are not lawyers and this is not legal advice. If you are planning something substantial, speak to your insurer first.
Common questions
Are PCD adapters safe?
A correctly specified, hub-centric, forged adapter, torqued properly and re-checked after fitting, is safe. A cheap cast one with no load rating is not. The failure mode is not gradual, which is why the quality of the part matters more here than almost anywhere else on the car.
Can I use a thinner adapter than 25mm?
Rarely. The adapter needs enough material to carry two sets of fasteners that do not interfere with each other. Below about 20mm there is not enough metal to do that safely, which is why adapters start where they do.
Will 5x108 wheels fit a 5x112 car if I force them?
No. People try, because 4mm sounds like nothing. The bolts end up loading the wheel unevenly, the seats wear, and eventually something cracks. Use an adapter or use the right wheels.
Do I need to re-torque them?
Yes. Torque the adapter to the hub, fit the wheel, then re-check both after about 50 miles. Clean the hub face before fitting — rust or grit behind an adapter causes run-out.
Will they affect my steering?
Pushing the wheel outward changes the scrub radius, so the steering can feel slightly heavier and the car may follow ruts more. At 25mm on most cars the effect is noticeable but not objectionable. Larger than that and it becomes a real change in feel.
Tell us the car and the wheels. Send us the make and model of your car, plus the car the wheels came off, and we will tell you exactly which adapter you need and whether the offset will work before you spend anything. sales@omiwheels.com or WhatsApp +44 7753 828059.
Browse the full range: wheel spacers and PCD adapters. Related reading: what size wheel spacers you need and the complete 5x112 guide for Audi, VW and Mercedes.