Dr. Miller replied:
Hey Em!
We don’t specifically test for that as our head impacts are to the helmet and thus the dial fit knob doesn’t come into play as they are below the test line. During helmet impacts the dial fit system does generally loosen and allows the helmet to decouple which is the desired outcome.
The dials are made of plastic and not all that durable when looking at impact energy and thus would likely just crack and break; especially if it’s on the occipital lobe (very hard bone)… Additionally the neck area has a decent amount of pliability so if that dial was impacted over the neck area the effects would likely be minimal when considering the entire injury event; much worse things would be in play! I suppose some lacerations could occur as the dial may break and scrape across your neck but those are not major concerns!
I like the dial fit helmets because the most important component when it comes to “fit” is making sure the helmet remains in place for that initial impact. Having the flexibility to adjust them for the wide array of activities, hair style, small adjustments for helmet size, … seems to be a benefit!
Hope this helps and let me know if I can further assist! Barry