Join Date: May 2016
Location: Green Bay WI
Year/Make/Model: 2003 Vulcan VN1600 Classic
Color: Pearl Ivory
Sometimes I use the helmet strap looped through the rear carrier or grab rail and then through the D-rings to at least hold the helmet onto the bike so no one can bump it and make it fall off the bike. If someone is determined or dick-head enough they certainly could just unstrap the helmet and do what they will, plus who is gonna ask them about it unless they saw the person who owned the bike put the helmet there. Even then most people would not say anything anyway, these days you never know what kind of nut cases are out there.
Probably the best options are to lock the helmet in the side bag or tour pack box if you have it, or to lock the D-rings to the bike in some manner. A thief generally won't waste any time/effort if they're deterred somewhat, they want to grab it quick and run.
When life throws you a curve, lean into it!