BS ISO 4251-1:2019 Code designated diagonal tyres (ply rating marked series) for agricultural tractors, trailers and machines Tyre designation and dimensions, and approved rim contours

Size coding
Loading
Dimensional tolerances
Dimensions
Contour
Wheel rims
Numerical designations
Width
Radial-ply tyres
Tyres
Pneumatic tyres
Agricultural tractors
Marking
Velocity
Diameter
Height
Wheels
Radius
Preferred sizes
Agricultural equipment
Vehicle components

Link: BS ISO 4251-1:2019 Code designated diagonal tyres (ply rating marked series) for agricultural tractors, trailers and machines Tyre designation and dimensions, and approved rim contours
Source: BSI Standards