Friday 15 May 2020

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How to find your tyre size

Tyres comes in a range of different sizes for all different makes and models of vehicles. These days we don’t often see a “standard” size tyre for certain vehicles any more. The size can vary from year of your vehicle to model of your vehicle.

For example;

2017 Toyota RAV 4

Tyre size options:

225/65R17

235/55R18

 

2010 VE Holden Commodore

Tyre size options:

245/40R19

245/45R18

 

The markings on tyre sidewalls may appear to be confusing. However, once you know the code they are in fact quite useful and can help ensure we are providing you with the right product.

We will cover the common ones that you need to know, so you can check your vehicle, and choose or supply us the details so we can get you the tyres you need.

WIDTH

This dimension refers to the distance in mm between side walls of the tyres.

PROFILE (Aspect ratio)

This number tells you about the section height of the tyre, by expressing it as a percentage of the section width.

So in the case of a 195/55 tyre, the section width is 195mm, and the section height is 55% of that.

The percentage is applied to the width of the tyre to calculate the height of the sidewall.

THE LETTER ‘R’

The single letter designates the type of tyre construction – ‘R’ stands for Radial, indicating the tyre has radial construction.

This particular design of tyre, the cords in side the construction are arranged from bead to bead at 90 degrees to the direction of the tyre movement.

This allows for flexible side walls, reduced rolling resistance and a softer ride. All on road tyres are a Radial construction.

RIM SIZE

Measured in inches this is the diameter of the RIM (the inside metal part of your wheel)

The rims on your vehicle obviously must match the rim size of the tyre to ensure a good air tight seal between the rubber tyre and metal rim

LOAD INDEX

This marking refers to load that tyre is rated for.

  • 81 = 462 kg
  • 82 = 475 kg
  • 85 = 515 kg
  • 86 = 530 kg
  • 87 = 545 kg
  • 90 = 900 kg
  • 91 = 630 kg
  • 94 = 670 kg
  • 95 = 690 kg
  • 100 = 800 kg

SPEED RATING

This letter refers to the “sustained speed” rating of the tyre.

  • N = 140 km/h
  • P = 150 km/h
  • Q = 160 km/h
  • R = 170 km/h
  • S = 180 km/h
  • T = 190 km/h
  • U = 200 km/h
  • H = 210 km/h
  • V = 240 km/h
  • Z = 240 km/h
  • W = 270 km/h
  • Y = 300 km/h

Watch our expert Pete explain the markings

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