First of welcome..
I am not certain I understand you correctly but if you are having vibration troubles and your sure the tires are balanced I would check the front rack second. Ball joints, Tie rods, and Center link among others may need to be changed at that mileage. Good luck.
1957 Dodge D100
1967 VW Microbus 21 Window
2004 Beach cruiser bicycle
"It cannot be emphasized too strongly or too often that this great nation was founded not by religionists, but by Christians; not on religion, but on the Gospel of Jesus Christ. For that reason alone, people of other faiths have been afforded freedom of worship here." Patrick Henry 1776