All that said, it's clearly true that the 1300 police bikes have a real problem with high speed weave.
Well, I've ridden over 16,000 miles in the last 90 days, in ALL weather and road conditions and usually fully loaded. In another thread about crossing the St Johns River at Jacksonville I was somewhat admonished here that my observations about a wobble or weave were probably incorrect.
Here's what I think after considering it fully... and observing a phenomenon of the ST1300 several times now. It WILL weave at speeds above 70 MPH when fully loaded with the windscreen down IF you are following another vehicles draft at the right spot. The first clue is a minor buffet following by the weave. It's a gentle movement, but if you have some crosswind buffet it CAN get out of hand if you are unprepared. I suspect the rider in question simply had his attention elsewhere when the weave started, he over corrected and induced the wobble himself.
Before you start throwing rocks at me... look again at my first sentence. I've LIVED with this bike every day for the past three months. I think it's the finest touring machine I've ever had. As a sport machine... can't tell. I've never had a sport machine and probably never will - I don't have the desire to drag a knee or toss the thing around the corners like it was stuck to a rail. BUT, I must admit, I've been on so many mountain roads lately and the thing rides so nicely that I must might find an available track day and take an advanced course just to explore those performance corners.
Back to the weave/wobble. I've noticed this even when some mini-vans are ahead of me. And with big trucks it's there sometimes and sometimes not. The effect of the wind stream seems somewhat lessened by the position of the windscreen - a high position seems simply to move the entire bike rather than induce any weaving motion. AND, I have actually practiced altering my seat position in these conditions. When I know I am entering a draft situation I can lessen the movement just by locking my knees to the tank and stiffening my upper body as I slightly relax my grip on the handlebars. It helps.
I think the ST1300 is VERY susceptible to even minor changes in your body position. Try this on your next day out. Pick a lonely road with a smooth surface and no traffic, of course. At about 40 mph just let the throttle drift down... or lock the throttle, and take your hands from the bars and sit upright on the seat. You are in balance almost immediately ... now drop a shoulder - doesn't make a difference which one. The bike will move accordingly... you can gently weave back and forth across the lane just by moving your shoulders.
If we all keep in mind that body position, wind buffet, angle of lean, and TIRES each have a significant affect on how the bike moves we will be better off - and better riders. Tires? Yes! I've seen a great deal of difference between the Dunlop RoadSmart and the OEM Bridgestone. Once the RoadSmart gets over on the side of the tire and into the different compound area it turns into a VERY sticky tire and much more willing to grip the road in all conditions. I'm actually beginning to ride into corners more aggressively just so I can be assured of better grip... but the down side of that is that even a small amount of gravel or debris will slide the rear tire very fast!
As to avoiding that 'weave' I see ... I worried at first but now I don't - it's a normal condition, at least for me and my bike. I just anticipate it and if the condition seems to get worse I just back off and bit from the draft or slow down. This should be how we ride ANY bike, regardless of the manufacturer or model - know how it reacts, don't be macho and say you can handle, be practical and explore the potential problem and KNOW you can handle it.
Leaving Monday for another 7,000 mile loop. Going through WV to PA and through NY to Maine and then back through New England states MD and VA.
Any of you want to ride with me for a few miles just send an email or PM.
Lee