With leverage, the front-most bearing that is at the front of the blower shaft, near where it attaches to the pulley, is the most loaded in the vertical axis, and the one in the front of the rotor beside it would be the least-loaded, in the vertical axis, of the front two bearings. The two rears would be a different load, as the front of the lobes "pulls" forward as the lobes force air backwards, and the rear of the lobes "pulls" downward due to their forcing air upwards.
So the most vertical load from air movement would be at the rear of the rotors, the most vertical load due to belt tension would be at the front of the pulley rotor, and some axial load would be exerted as the rotors pull air backwards, so the bearings all receive different load profiles and aggregates, and it varies based on boost and RPM. also, they are not turning the same speed, as the pulley rotor goes 3/5 the speed with its five lobes as does the non-pulley rotor with its three lobes.
Also, the gears provide some lateral load as the gears repel each other, as gears tend to do, but that is not significantly negative-due-to-leverage transferred to the front bearings, because they are so far, in relation to their centerline versus the distance from gears to rear bearing centerline, from the gears.
To sum up:
Vertical loads: front bearing due to pulley and rear bearings due to thrusting air upwards, also against pressure. No appreciable vertical load on front non-pulley bearing.
Axial loads; absorbed entirely by the rear bearings
Lateral loads: from air trying to push rotors apart, all four bearings will experience this, and also lateral load from gear mesh in the rear primarily on the rear bearings, as the gears try to repel each other due to tooth shape needed for most effective gear mesh/energy transmission.
