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Rim Diameter Size Guide

Wheel Diameter 

Example: 6.5x15
Explanation: 15 is the wheel diameter and 6.5 is the wheel width
Notes: The larger size of the two is normally the diameter, with the smaller being the  rim size


  • Wheel diameter is referred to in inches. 
  • Diameter of the 'rim' in inches (excluding the tyre).
  • Standard road cars generally have wheels that are between 14 inch and 19 inch in diameter.
  • Luxury, sporty cars, SUVs and 4x4 vehicles generally have the bigger size wheels.

Rim Size Guide - Wheel Width

Wheel Width

Example: 6.5x15
Explanation: 6.5 is the wheel width x 15 is the wheel diameter
Notes: The smaller size of the two is normally the width, with the larger being the diameter

  • Wheel width is referred to in inches.
  • The width of the wheel will dictate the tyre sizes that will fit on the wheel.
  • The wider the width, the wider the tyre size that will fit on the wheel.
  • Example: 6.5x15 will normally fit a minimum tyre width of 185, an ideal of 195/205 and a maximum tyre width of 215. Depending on the alloy wheels and vehicle body.
  • Wider wheels and tyres gives your tyres better grip on the road, giving your car better roadholding and braking than tyres that are narrower.

Rim Size Guide - Wheel Offset

Wheel Offset

Example: ET38
Explanation: 38mm distance from the centre of the wheel to the mounting face
Did you now: 'ET' is derived from the German word 'Einpresstiefe', which translates to 'insertion depth'

  • Wheel offset is measured in mm and determines how far the wheel will stick out.
  • Offset with a minus indicates a negative offset e.g. "-12", while the absence of a minus indicates a positive offset e.g. "ET38".
  • Zero offset: mounting face is exactly centre within the wheel.
  • Positive: mounting face is positioned further outbound from the centre.
  • Negative:  mounting face is further inboard from the centre of the wheel.
  • The correct offset is highly important. The wheels wont' fit if you stray too far outside of the correct measurements or catch on a fender / brake calipers.

Rim Size Guide - Wheel Bolt Pattern PCD

Bolt Fitment - PCD

Example: 4x100
Explanation: 4 bolts in a 100mm diameter circle
Notes: 'PCD' stands for 'Pitch Circle Diameter'

  • PCD is the diameter of an imaginary circle which passes through the centre of all the wheel bolts / lug nuts.
  • The diameter of the circle is measured in mm.
  • Vehicle bolt patterns are normally 4, 5, 6 or 8 lug holes depending on the vehicle make & model.

Rim Size Guide - Wheel Centre Bore

Centre Bore

  • The size of the centre hole in the middle of the wheel. 
  • Measured in mm.
  • Normally covered by a centre cap.
  • The wheels won't fit if the centre bore of the wheels are smaller than that of your car's.
  • Spigot rings needs to be fitted, if the bore is larger than that of your car's.
  • Spigot rings allows the wheel to be firmly centred on the hub.

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