There's a lot of confusion about why we use such big tires. It's commonly believed that a bigger tire has a bigger contact patch. This is incorrect. An ST1300 fueled up weighs about 700 pounds; the rider is about another 200. The tires are at about 40 psi. So, 900 pounds divided by 40 psi is 22 square inches. If the weight is equally distributed on the two tires, each tire has a contact patch of 11 square inches. That's it, tire width and diameter never entered into the calculation. A narrow tire will have an 11 square inch contact patch that's long and narrow; a wide tire will have an 11 square inch contact patch that's short and wide. If you drop the tire pressure to 20 psi (popular for on/off road bikes) then your contact patch doubles in size. If you find yourself in snow or rain, raising the tire pressure will shrink your contact patch and help you push through to the road.