I am thinking that if it was worn steering components, it probably would not resolve and probably would not have come on so acutely. But I will check that out for sure. Thanks.
Generally true. But steering can be a 'Threshold' system. Works fine up until it gets just past the point where, under certain stress, it starts to give issues. Or, a single pothole, etc, can create an instant problem.
Tires/Wheels
Tire cord separation. Probably not because it should give you other signs. But possible.
Tire balance. Has one or both tires thrown weights? Are they cupping or showing uneven wear?
Air pressure (which you've already eliminated).
Bent wheel. This takes a very big impact. Like a pothole that would do damage, not something that you wouldn't notice at the time.
Brakes
A caliper or pad hanging up. Check for uneven pad wear. This can be a good indication if it has been going on for a while.
Spin the wheel and look for any intermittent binding on the rotor. This can indicate a warped or damaged rotor. A Dial Indicator or Runout Gauge is very handy for this if you have one. This will give you an exact measurement on the amount of variation. Some is allowed.
Steering Components
Lift a wheel. With the handlebars secured (ratchet straps, someone holding them, etc.), grab the wheel front and back and move it left to right. Do this for both sides. Look, listen, and feel for any unwanted movement.
I doubt that it is your steering 'DPS' unit.
Check handlebar play. The universal joint can wear (not uncommon). If your handlebars move very far without resistance, this is a definite indication. A sloppy universal joint combined with other front end issues can also give you the symptoms you are experiencing.
