What you’re looking for is the sum of the static forces on the front axle; depending on where your weights are located you’re looking at likely a force load and moment loads in up to 2 axes.
Cbenson’s formula above is correct and can be used to determine the forces on your axle. However don’t forget that this is a static exercise, not dynamic! It will not take into account forces acting upon the axle due to driving the axle [with a motor].
Ryan Barnes, E.I.T.