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Wheel (Rim) Size Guide for Beginners '.

Not all wheels will fit all cars!

This basic guide below explains rim sizes when buying alloy wheels for your passenger car, sports car, 4x4 vehicle, bakkie etc. Understand wheel diameter, width, offset, bolt fitment and centre bore before shopping for wheels.


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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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