Alloy Wheel Sizes Explained, Blog

Alloy Wheel Sizes Explained

Alloy wheels are a favourite among car owners looking to upgrade the appearance or performance of their car. Getting the correct size alloy wheels for your car is absolutely important if you are planning to get them for your car. Buying a set of alloy wheels that fit correctly is important else it may cause problems while driving.

In this blog, we will discuss how to measure alloy wheels and get the perfect set for your car.

Why fit alloy wheels?

Before we discuss the right size of alloy wheel for your car, let us look at the necessity of having alloy wheels. The advantages of having an alloy wheel are:

  • Improves the appearance of a car
  • Alloy Wheels are light
  • Precise steering of vehicles
  • Reduces fuel consumption
  • Eliminates the risk of brake failure

Different Measurement on an Alloy Wheel

The format for typical alloy wheel measurement for example is 20 x 8.5J, where 20 stands for wheel diameter and 8.5J is the wheel width. Now comes the tough part, how to measure the wheel diameter and the wheel width?

  • Wheel Width Measurement: Also known as wheel rim width is the distance between the outside and the inside lip of the wheel. We usually measure this in inches and the compatible wheel width range differs from vehicle to vehicle. Alloy wheels come in a range of different wheel rim width so we can safely say that a one-size-fits-all solution won’t work here.
  • Alloy Wheel Offset Measurement: One of the most important alloy wheel measurement which is in millimetres, and it is the distance from the hub-mounting surface to the wheel’s true centre line.

Let’s take an example of an offset measurement of ET40. Here the offset shown is 40mm. A few indications of offset calculations are:

  • Low offset number: Wheel will sit further out from the vehicle
  • High offset number: Wheel will sit closer in from the vehicle
  • Very Low offset number: Wheel will stick out too far from the vehicle
  • Very High offset number: The wheel may touch the suspension or the body of the vehicle.

Wheel offset sizes are not fixed for vehicles, but they have a particular range and that differs from vehicle to vehicle.

  • Wheel Pitch Circle Diameter Measurement: The shorter version is PCD, and it is measured in millimetres. It is the measurement of the space between opposite bolts holes that are on your wheel.
  • Wheel Centre Bore Measurement: The measurement of the big hole right at the centre of the wheel and sits on the mounting hub of the vehicle. This usually measured in millimetres.

Leave the Hard Part For Specialists

All these measurements can turn very tricky and it is best left for a wheel specialist or a garage. This blog was to give you an idea of what are the different measurements so that you understand your wheel specialist or garage technicians when they talk technical.

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