I built up a budget set of "fat bike" wheels for my Troll, mostly out of curiosity. The rims are made by Weinemann and are 65mm wide (same as Surly's Large Marge and Marge Light) and about 1/3rd the cost. Surly really means it when they say "fatties fit fine" as these actually fit really well. To get around the brake bosses you have to put the rims in with a deflated tire and come at them at a bit of an angle (will not work with a rack installed) but once in they have plenty of clearance with most tires labeled 2.3" to 2.5", the front derailleur may rub just a tiny bit but it could be solved with getting a pair of monkey nuts from Surly.
On the snow and sand there was a large improvement in float, obviously not quite what a "true" fat bike would be but certainly a big improvement. Remember, before fat bikes came around Iditarod racers were using much narrower Snow Cat rims with success.
A couple racers needed some last minute wheels before heading to the USA BMX Nationals in New Mexico this weekend. Looking forward to seeing how this weekend goes because 3 of my wheelsets have a very good chance at making the podium, I have built wheels for nearly all of the Blaze Factory Team now which is very exciting knowing how strong their lineup is!
Obsession, or passion? Who am I to judge? Either way I simply love building wheels for those who appreciate quality!