How to choose
Why a wheel needs a ring
Alloy wheel manufacturers usually machine the centre bore (DIA) larger than the car's hub. The reason is simple: one wheel design has to fit many car makes, and each of them has its own hub diameter. A centring ring fills the gap. It is pressed into the wheel's centre bore from the back and leaves a hole exactly as large as your hub needs.
Modern cars usually centre the wheel on the hub, not on the bolts. If a gap is left between the hub and the wheel, the wheel can end up bolted on slightly off centre. Rial says that the driver then feels an imbalance, especially at high speed. Most often it shows up as vibration in the steering wheel.
What a ring does and does not do
A ring is not a load-bearing part. It helps you seat the wheel precisely in the centre while you tighten the bolts. The wheel manufacturer Schmidt calls it a fitting aid: once the wheel bolts are tightened, they are what holds the wheel to the hub. So a ring is no substitute for the right bolts. The wheel still needs bolts or nuts with the correct thread, seat and length, tightened to the torque the car manufacturer specifies. Rial recommends checking and retightening the bolts after about 50 km.
How to read the size
Centring rings carry two sizes, for example 72.6/57.1. The first number is the outer diameter, which has to match the wheel's centre bore. The second is the inner diameter, which has to match the car's hub. In the listing you can select them with the "Outer Ø" and "Inner Ø" filters.
- You will find the wheel's centre bore in the wheel specification. Borbet, for example, states the correct ring in the technical documentation for each wheel.
- Get the hub diameter from the car manufacturer's data or from a dealer. These are exact figures with a decimal, and 57 is not the same as 57.1.
If the wheel's centre bore is exactly the same as the hub, you do not need a ring. This is the case, for example, with the car manufacturer's original wheels. If the hub is larger than the wheel's bore, a ring will not help, and that wheel does not fit your car.
Plastic or aluminium
Rial writes that centring rings are mostly made of plastic, though some are metal. Wheel manufacturers make different choices here: Borbet produces coloured plastic rings, while BBS and AUTEC use machined aluminium rings, and AUTEC also gives them an anodised coating against corrosion. If the wheel manufacturer specifies a particular ring for its wheel, choose that one.
Fitting and quantity
You need four rings, one for each wheel. The ring has to go all the way into the wheel bore. AUTEC's fitting instructions say that a correctly fitted ring sits slightly below the wheel's mating face and must never protrude. If a ring is hard to push in, manufacturers recommend soap or tyre fitting paste, but not oil or grease. Before mounting the wheel, check that the ring is in place in all four wheels.