Ply Rating, Load Index and Speed Symbol: What 20PR / 160 / L Actually Means

13 November 2026 · Tires

Three numbers on the sidewall decide whether a tire is legal and safe for a given axle load. They are often quoted incorrectly in enquiries, and a wrong load index is the kind of error that only shows up when the vehicle is fully loaded.

The three values

Dual fitments are written with two load indexes, for example 152/149: the first figure applies to single fitment, the second to dual fitment.

Load index reference

These values are the standard index table; always compare against the axle load in the vehicle documentation and the local regulation, not against a generic chart.

Why ply rating still matters

Ply rating describes casing strength and how much the tire can be loaded and re-inflated. A 16PR casing run at 20PR pressure is not equivalent, and a 20PR casing run under-inflated will fail early even if the load index looks sufficient. On mining and on/off-road work, the casing takes impact loads that a highway pattern never sees.

Speed symbol in practice

Most heavy truck tires in this catalogue are L (120 km/h) or K (110 km/h). Speed symbol is a sustained-speed limit at rated load, not a target. Regional and mixed-service trucks that rarely exceed 80 km/h still need the symbol matched to the vehicle's declared maximum speed.

Examples from the catalogue

How to check an enquiry

1. Size from the sidewall.
2. Required load index from the axle load, divided by the number of tires on that axle.
3. Speed symbol from the vehicle's maximum design speed.
4. Dual or single fitment — it changes the applicable load index.

If you send only a size, we will quote a standard load index for that size and tell you what we assumed. We will not present an assumption as a confirmation.

Browse patterns with full load index data · Send your axle loads