Tires: tire, duty tires, radial tires

Question
what is diference diagonal and radical ?
Which one for the best loading ?

Answer
Meng,

I think you mean "diagonal" - also referred to as "bias" - and "radial" - not radical - properly called "radial belted".

Bias tires are the old way of building tires where the ply fabric is applied at an angle - bias - to the direction of travel.

Radial tires are always belted, and the ply fabric is 90 degrees to the direction of travel - the radial direction as opposed to the circumferential direction.  The belts are at a bias, but a much steeper angle than a bias tire's ply fabric.

Neither is better for loading.  This is more a function of the construction itself.  But it is fairly common to see heavier duty tires in bias simply because they are easier to build than radial tires - and are therefore less expensive.