Originally Posted by CanadianX
I have a windshield and not although not a giant am 200lbs and I still get the head shake. More to follow once I play with sag and check the fender alignment. I did set sag when new but things may have settled out since then.
The 690's have adjustable (two settings) triple clamps. As delivered, they are set to max offset (less trail). Using the smaller offset increases the trail and should improve stability at speed. You can easily check which setting by removing the triple clamp cap (don't loosen the pinch bolt). If the dot is at the rear, they are set to max offset. Changing offset requires disassembly of the front end and gives an opportunity to grease the steering head bearings.