Sometimes it's the tire, other times it's not.
Local Kawasaki shop was having issues with a vibration above 40 mph on a couple police motors.
They replaced the steering head bearings, and adjusted them, replaced the fork oil, brake pads, tried two different tires (also Michelin), fiddled with the preload adjustments, checked the fork alignment, took apart and cleaned the calipers, replaced the wheel bearings, and just kept throwing money and parts at these bikes hoping something would fix them. No luck, vibration at anything above 40 mph.
I discovered what was causing the vibrations without removing or replacing a single part.
The spools (bobbins) on the brake rotors were jammed up tight with brake dust, sand, and road grime.
A simple flange head nut and bolt set up, through the spools, spun them while I sprayed them clean with brake cleaner.
No more vibration.
The spools being jammed up, turned the rotors into a warped piece of metal, riding on the brake pads, shaking the front end like a dog shaking off water.
Sometimes you just have to think outside the box when your problem solving stuff.
And yes, the spools on your ST would benefit from doing this every few months.