Grinding wheel assembly is laid on four green idly rollers.
If the assembly is static imbalanced, the gravity turns it to the position at which the center of mass is below the assembly axis.
Move pink contra-weights in circular dovetail groove of the assembly to upper positions and fixed them there for equilibrating, then test the assembly again.
The structure of four roller helps to reduce the friction in rotary motion of the assembly to the least amount (in comparison with the assembly revolving in an ordinary bearing).