Installing fat bike tires on a BSO for winter riding(condition of averaging -23 C for 2*17km). Is it doable, safe? As for my other question Winter riding: Is it safe to ride on a BSO/cheap bike at temperatures below -15&#176;C on icy or damp roads? I've got a lot of suggestions of getting studded tires for winter roads. The road I take is not very well maintained and there's a lot of bumps and ice... and salt. BUT! I still haven't abandoned my plan of commuting in winter Montreal. Though I haven't seen anyone mentioning fat bike tires. The idea came when I went window shopping for studded tires prices and saw fat bike tires as a cheaper investment. Although I do not know whether it is feasible or not to install them on my BSO.  My BSO is 21" and I will need to ride 2*16 km everyday (commuting).
Fat bike tyres (3.8" or bigger) are unlikely to fit in the frame or fork of your BSO.  In addition, such large tyres require wider rims (typically 50-100mm internal width) which you are also unlikely to have.  Finally, fat tyres have their advantage in 'floating' over sand or snow, however they won't grip on ice as well as a studded tyre.