How To Read A Tyre

how to read a tyre

Tyre Designations
DIMENSIONS EXPLANATION
300-4 Tyre width 300 / Rim Diameter 4"
10x3 Former designation in inches:
Tyre Width 3” / Tyre diameter 10” ( =3” x 2 + 4”)
260x85 Designation in millimetres:
Tyre diameter 260mm / Tyre width 85mm
The former designation in inches converted to mm:
10” x 25.4 = approx. 260mm
3” x 25.4 = approx. 85mm
85/100-4 This is how the designation would be, had it been a passenger car tyre.
Tyre width 85mm / Profile 100% / Rim diameter 4”.
10x3.00-4 American designation, mainly used for low profile and turf tyres:
Tyre Diameter 10” / Tyre Width 3” / Rim diameter 4”


>>Download full Treadway technical information document
 

LOAD AND SPEED RATINGS
On the sidewall of a tyre you can find the load index and speed symbol following the key sidewall size markings.
 
  • The Load Index is a numerical code associated with the maximum load a tyre can carry
  • The Speed Symbol indicates the speed at which the tyre can carry a load corresponding to its load index.
>>Download full Treadway technical information document
 

PLY RATINGS
Originally, tyres were marked with the exact number of canvas layers (plies) built into the tyre. This was an indication of the strength of the tyre. As stronger materials were developed, the number of layers could be reduced - maintaining the same strength of the tyre.

The designation ”Ply Rating“ therefore does not indicate the actual number of layers (plies) in the tyre, but the number of layers originally required to give the desired load capacity. When working with PR marked tyres, the actual manufacturers data must be used to determine the load capacity in kg (or pounds).

>>Download full Treadway technical information document to see load equivalent of different ply ratings.



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