Originally Posted by froze
Also as another poster mentioned the position of the computer magnet will have a major effect and should be opposite the valve.
That's not what dannoXYZ said. Actually the rim seam is usually the heavey side of the wheel and the seam is opposite the valve. Except for very long valves like the 60mm valves that Wil Davis mentioned the weight of the valve may not enough to offset the weight of the seam.
From my experience I'd say that rim seams, valves, and magnets do not have a big effect on wheel balance.
I think radial wobble is more often caused by tires not properly seated, wheels out of true radially, and defective tires.
Al