Tyres come in three types of markings essentially:
| IMPERIAL
The Imperial system comes to our shores mainly from America. This is how the system works - |
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31 | Overall diameter in inches |
| 10.5 | Tyre width in inches | |
| R | Means Radial Ply construction | |
| 15 | Tyre diameter in inches | |
| LT | Means Light Truck designation | |
| 109 | Is the load index which equates to 1030 kgs for a single wheel | |
| S | Is the speed rating of 180 kph | |
| METRIC
Metric markings are found on tyres arriving from Japan and some European manufacturers - |
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LT | Means the tyre construction is Light Truck designated |
| 235 | Relates to the section width of the tyre, in millimetres | |
| 85 | The Aspect Ratio of the tyre, being 85% of the section width of the tyre at the correct pressure | |
| R | Means Radial Ply construction | |
| 16 | Diameter of the tyre, in inches | |
| 115 / 113 | This is the Load Rating and depends on whether a single or dual tyre application is used. 115 equates to 1215 kgs | |
| N | The Speed Rating, equal to 140 kph | |
| ALPHA NUMERIC
We still see some of these markings around and it works like this - |
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G | The code for maximum load |
| R | Radial Ply construction | |
| 78 | This is the Aspect Ratio | |
| 15 | Rim diameter in inches | |
| LT | Light Truck construction | |
Used with kind permission from 4x4 Australia Magazine
Copyright 1998
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