FWIW, 1Up also sells spacer kits to accommodate fat tire bikes up to 4.9” wide and they will also work with standard bikes. However, 1Up's new XTtreme Duty version rated for off road use can now fit tires up to 5.25”. The tires in the image are 3.8s but I run 4.5 studded versions during the winter months.
NOTE: The original 1Up wheel locks are not long enough to span the full width of the spacer kit so one must either acquire the longer fat tire versions or use a standard cable lock to secure bikes to the rack.
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Rival Quikrstuff rack will fit tires up to 5” without the need for spacers but costs more than the 1Up HD/SD versions. The name of the rack is a bit of a misnomer as the lead time in acquiring one is up to 8 weeks. Still, a quality product.