Back from Canaan Valley WV X-country skiing

When you are towing on snow and ice, as offgrid points out, coefficient of friction is what really matters. But if there is ice, increasing the coefficient of friction is more complicated.  Studded snow tires and chains help in these conditions  to the extent they break the surface of the ice and partly eliminate the very thin film of water on top of the ice that makes it slippery, while mechanically cutting into the ice, thus increasing the surface area that is in contact with the surface on which you are driving and increasing your coefficient of friction.  Towing capacity is not the measurement that applies to this circumstance.