How to know when to change front tires on 4WD tractor?

[Texasmark]

I air mine based on ground contact. On any tire, car or tractor, if its wearing heavy in the center, its overinflated for the load. It puffs up like a round inner tube & only the center is making good contact with the ground. Deflating it a bit will give it a more square profile, better traction & even wear.

That's a problem belted tires help to overcome. I noticed it back when the US stubbornly went to bias belted tires before they finally copied the Europeans that had been running steel belted radials (Michelin for one) for seemingly EONS!