Off-road longboards with pneumatic knobby tires are fun on downhills, but like the difference between a mountain and road bike, the flexion of the tires and rolling resistance of the treads would seriously cut into the range on a Boosted Board.
The urethane wheels on a skateboard, longboard, or roller blades are really very efficient.
Fair points, and I was thinking something that looked more like a DOT legal "racing compound" [1] than an all out "Off Road" knobby tire. That might need a bit of 'suspension' though to work effectively, I'm not certain. Sidewall flex to consider/design/etc. Yet another thing I've seen would be an integrated tire/wheel/flex approach like shown in some larger scale, experimental use cases [2].
Also, wouldn't higher grip/friction ratios enable using less tire material to get the same contact patch/grip otherwise achieved? Kind of seems like a logical hypothesis to me, though if there's a reasoning flaw hey would be game to see it for sure!
Decreasing the tire size increases the internal air pressure and ground pressure (a problem if you want to go over dirt), but modern tire construction is up to the task.
Also, grippier rubber is usually a trade-off between tread wear and friction. Though with the price of a Boosted board, I imagine their customers would prefer more grip and a few percent of their purchase price for new tire replacement every couple hundred miles.
The urethane wheels on a skateboard, longboard, or roller blades are really very efficient.