For those of you not familiar with them, these are snow bikes. They have specially designed wheelsets that can float through snow and other soft surfaces.  To accomate the wider tires, the frame, fork, and bottom bracket have to be specially designed also.  The typical mountain bike tire is 2.1".  These tires are 3.8" and have three times the volume of most tires and are run at 1/3rd to 1/5th the air pressure as most mountain bike tires.  The hubs are 135/170mm wide and the 82mm rims are 3x the width of the typical rim.

The wheels on these bikes are pretty heavy but this particular model has lightweight rims (well, they're still 900 grams) with holes in them as well as 120TPI tires, which makes for a lighter tire.  The wheels are heavy but not as much as you might think.  Same goes for how the bike rides, not as ponderous as you might think.  While bought primarily for winter, it's still a lot of fun to ride on the dry trails.  Those big tires can really soak up a lot of abuse.  I've ridden winter trail with my conventional MTB but do look forward to seeing how these bike will fly down the snowy trails.