Steer
The steer axle carries the front of the vehicle and does all the steering. Rib patterns with solid shoulders give directional stability, even wear and predictable handling. Irregular wear on a steer tire shows up immediately as vibration and poor tracking.
Drive
Drive tires transmit torque, so they need traction: block or lug patterns with deeper tread. They wear fastest and are the position most worth regrooving and retreading, provided the casing has been protected by correct pressure.
Trailer
Trailer tires are dragged rather than driven. Free-rolling rib patterns with strong shoulders resist scrub in tight turns and give the lowest rolling resistance on the vehicle. Fitting worn drive tires to the trailer is common and usually false economy.
Rotation
A written rotation plan by position, agreed with the fleet, extends the life of the set and keeps wear even. It is part of the specification, not an afterthought.