Wheel Spacer Size & Fitment Guide.
PCD, offset, and thickness explained.
Fitment is the number one thing people get wrong with spacers. This guide covers everything you need to select, buy, and install the right spacers for your car — no guesswork, no expensive mistakes.
What is the Meaning of PCD (Pitch Circle Diameter)
PCD stands for Pitch Circle Diameter — the measurement that defines your wheel's bolt pattern. It consists of two numbers: the quantity of bolts and the diameter of the circle they sit on.
Common examples: BMW uses 5×120 (five bolts on a 120mm circle), Audi and VW typically use 5×112, Porsche runs 5×130 on most models. Getting this wrong means your spacers won't bolt up at all — PCD is non-negotiable.
Measuring PCD yourself is straightforward. For five-bolt wheels, measure from the centre of one bolt hole to the centre of the bolt hole two positions away, then multiply by 0.85. For four-bolt patterns, measure diagonally across opposite bolt holes. You can also find the spec in your owner's manual, on wheel manufacturer websites, or stamped on the back of your existing wheels.
Centre Bore (CB) and Hubcentric Fitment
The centre bore must match your car's hub diameter exactly. This is not a "close enough" measurement — even 0.1mm difference causes problems.
Wrong centre bore sizing creates wheel wobble and unsafe fitment. The wheel won't sit concentrically on the hub, leading to vibration that gets worse with speed. In severe cases, this causes premature bearing wear or wheel separation.
Hubcentric design maintains the original load distribution your car manufacturer engineered. The hub carries the vehicle's weight, while bolts provide clamping force. A hubcentric spacer replicates this relationship exactly — the hub still carries the load.
Non-hubcentric spacers rely on bolts to centre the wheel. Bolts are designed for clamping, not centring. Every Brightstone spacer is machined to match your exact hub bore, so the wheel centres on the hub lip just as it does from the factory.
Spacer Thickness: Choosing the Right Size
Spacer thickness determines how far your wheels move outward. The rule of thumb is simple: offset change equals spacer thickness. If you want your wheels 15mm further out, you need 15mm spacers.
Subtle stance improvement and minor brake clearance gains. Works well for cars that just need wheels to sit slightly more flush with the arches without dramatically changing the look.
Good for: stock-height cars, minor offset correction
The sweet spot for combining improved handling with a noticeably better stance. Provides the best balance of performance and aesthetics for most street cars. Most Brightstone orders fall in this range.
Good for: daily drivers, performance road cars, most European models
Creates aggressive stances. Requires careful consideration of arch clearances and suspension geometry. May also function as a PCD adapter when combined with a different bolt pattern on the outer face.
Good for: show cars, track builds, wide-arch applications
Offset Correction Explained
Wheel offset (marked as ET numbers) describes how far the wheel's mounting surface sits from its centreline. Positive offset means the mounting surface is toward the outside face of the wheel — the wheel sits further into the arch.
Spacers reduce positive offset by moving wheels outward. This improves stance, increases brake clearance, and widens the track.
Example: ET45 wheel + 15mm spacer = ET30 final offset. The wheel sits 15mm further out from the hub than it did before.
Most cars benefit from 10–20mm offset reduction for improved stance without affecting handling or clearances. Excessive offset changes — particularly beyond 25mm without checking arch clearances — can cause tyre rubbing at full lock or full suspension compression.
Even two cars of the same model but different build years or trim levels can have different clearances. Measure the gap between your tyre and arch lip, check clearance to suspension components, and verify at full steering lock before committing to a thickness.
Real-World Examples
These examples show how the same thickness affects different cars differently. Always measure your specific vehicle rather than copying someone else's setup.
Bolt Length and Hardware Matching
Extended bolt length must equal your original bolt length plus spacer thickness. Insufficient thread engagement is dangerous and can lead to wheel separation.
Seat type matters as much as length. Conical (tapered) seats are most common on European cars; ball seats appear on Porsche and some others. Using the wrong type prevents proper clamping and can damage wheels.
Torque specifications remain critical regardless of spacer thickness. Most cars require 80–140 Nm depending on bolt size — always check your owner's manual. Under-torquing allows loosening; over-torquing strips threads or stretches bolts.
Always use grade 10.9 or 12.9 bolts. Cheap bolts can fail under the cyclic loads that wheel fitment creates.
Example: 28mm OEM bolt + 15mm spacer = 43mm minimum. Round up to next standard length.
We supply the correct extended bolts matched to your spacer thickness and vehicle spec with every order. Nothing to source separately.
Finding the Right Wheel PCD
The wheel PCD needs to match the hub PCD for wheel spacers to fit. If it doesn't, hub adapters can convert one PCD to another — but for standard spacers, PCD must match exactly.
You can find your car's hub PCD in your owner's manual, on the back of your existing wheels, or via a fitment database like Wheel-Size.com which covers virtually every make, model, and year with accurate PCD and centre bore data.
| BMW PCD | 5×120 (E/F-series) · 5×112 (G-series) |
| Audi PCD | 5×112 |
| Mercedes PCD | 5×112 |
| Porsche PCD | 5×130 |
| VW PCD | 5×100 or 5×112 depending on model |
| Aston Martin PCD | 5×114.3 (classic) · 5×128 (modern GT) |
Mistakes to Avoid When Choosing Spacers
Correct fitment, machined in-house, every time.
FAQ: Wheel Spacer Fitment
Find spacers for your car
Every Brightstone spacer is machined to match your PCD, centre bore, and hub. Extended bolts included. UK-made, hubcentric, lifetime warranty against defects.
