Originally Posted by
Mr. 66
Check the seatube alignment to the bb driveside, then downtube to the same bb face, then the headtube to the seatube. The string test only tells you something is out it won't be accurate for the rear needs unless the front is in check.
I went and did what mr. 66 said. Tubes are align to my eye, but I found out something else.
The chainstays are only tubes with lugged joints. All other tubes are welded. Crank-side lug is farther from the side of the BB. Maybe because of chainring clearance? Chainstays are not dimpled. Left-side lug starts from the edge of the BB. The difference is max. 1.5 mm.
I will try to align rear triangle couple of millimeter to left and share the outcome after that.