Minimizing the variation in road force that is caused by a combination of wheel runout and variation in tire stiffness around the circumference.
Merc wheels have a faint white dot that should be matched with the red dot on the tire. This matches the low spot on the wheel with the "high spot" on the tire, which is usually the point of maximum radial spring rate.
What you describe as road force variation is usually called radial force variation, and it can cause wheel shake similar to static unbalance. Whenever you have new tires installed, carefully clean the wheels and find the faint white dots, then instruct the tech to matchmount the white dot on the wheel and red dot on the tire.
If you have an insoluble wheel balance problem, have the wheels/tires analysed on a Hunter 9700. Look to achieve less than 10 pounds radial force variation. Amounts in excess of this can usually be corrected by re-indexing t the tire on the wheel to match the measured low spot on the wheel with the maximum radial force. The Hunter 9700 will also tell you if the wheel is out of round or the tire has excessive radial force variation, so if you can't get a good "balance" you have to replace either the wheel or tire.