Mickey2

It should not be a problem finding an all seasons bike. The challenge with winter is usually frost and gearing parts; wires, cable housing and moving joints have be given the chance to dry up between uses. Snow build-up on the gear arm can happen. The second thing I can think of is finding a tyre you like for snow and icy condtioins; a rough pattern for snow grip, maybe spikes if there's hard ice. You can usually find a good selection for 26" and 28" rims, and the frame has to take the width you choose.

Around 47 m.m. width is plenty enough for most on and off road use. and the right type of treading pattern should cope with muddy roads. I don't think I ever have exceeded 50 m.m. width. I don't know if you use fenders, but make sure there is plenty of room between fender and tyre, you might need to poke out snow build up if there's loose snow and it's just above the point of frost. You can get a new bike, but just as easily fix up and old bike with 559 rim wheels. A lot of people keep a winter bike because it's much harder on the bike, and it can be a good idea to have at least 35 m.m. tyre width in frost, snow and salty conditions. It needs a bit of extra upkeep, but it doesn't have to be something very special. Your Vaya might be the ideal all round build to begin with.

I have to add that I have only test ridden fat bikes and have no idea about their finer points, but I know you should be able to fit a more regular bike with suitable tyres and rims for the job. If you are interested in trying out fat bike tire dimensions, this should not prevent you from further experimenting. Like with all bikes, the componets make a difference, the type of frame you like, gears, etc. I guess a more expensive bike taking 55 mm width tyres can turn out to be the better one in the long run, but it all depends on the qualities you look for in a fat bike. Some of my favorite bikes (for completely different riding) have been vintage fix up bikes that cost much less money than a higher quality new bike. To many factors are involved to give any straight forward advice. Someone with a fat bike will hopefully reply to the tread ;- )