In winter we would use touring skis instead of bikes.
Bikes are fun in the snow too
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Coming from a mountaineering background like you though I am always disappointed/shocked at the complete absence of mountain craft in the mountain biking magazines. You'll see nothing in them about carrying a survival bag and whistle & torch, compass and map reading skills, clothing etc that you would in the mountaineering magazine. Most mountain bikers set off woefully unprepared IMO.