Nextie has a couple of double wall options. Be sure to haggle with them for a 20% discount.
Are people really running 27.5 rims with big (even by fat bike standards) tires in the snow?
Absolutely. As grooming has improved in certain hotspots here in Maine (Gorham, Bradbury state park, York Hill Farms, Carrabassett Valley), the trend has moved away from the tankiest possible setup with super wide 26” rims and 5” tires with super deep paddle treads such as the Surly Lou…evolving toward 27.5” wheels with 4.5” tires and better rolling tread.
It’s a lot like the difference between 27.5 and 29 MTBs…you find that less rim and tire/tread will get the job done with bigger wheels. Even where floatation matters, though good grooming greatly reduces the need for that. A more summer-like fat bike is the best way to experience good grooming conditions.
Also, running slightly narrower tires means I can finally stop running 190mm crank axles. Those are really brutal on the knees. I’m looking forward to my first year on a 170 crank axle and 27.5 fat wheels. I think I’ll be able to do more miles — even if I ride less in bad conditions without the ability to act as my own groomer like I do sometimes with 5” tires — and take less of a beating.
Ambitious fat biking in snow can really take its toll on anyone’s body and I’m a disabled rider with severe arthritis among other things…