Build the force requirement first
Add rolling, slope and acceleration forces for the design event. If two powered wheels share force equally, each supplies half, but only when normal load, wheel diameter and control command support that assumption.
Translate force to torque
Multiply force at each wheel by effective rolling radius. A larger drive wheel requires more torque for the same tractive force but travels farther per revolution.
Continuous versus peak
Peak torque may handle a start or short ramp. Repeated operation is limited by motor, controller and gearbox temperature. Define both peak event and continuous duty before selecting components.