Originally Posted by Push370zzz

It is most certainly all in your head. The spacers weigh what...1lb or 2lbs? Unsprung weight, such as that from a heavy wheel/tire combo, is bad because the weight is concentrated 8-14" away from the center of the hub. The further away from the center of the hub, the greater the effect. Your spacer's weight is concentrated an inch or two away from the point of rotation. There is just no way that two spacers weighing that little are noticeable.