My company designs and builds underhung cranes and monorail systems. One of our product lines is a monorail tractor with a 16" dia. poly drive tire. See the attachment. The standard bores for this tire are 1.250", 1.438", and 1.625". There may be a case due to HP that a 1.938" dia. bore is required. It has been proposed that the existing casting be used, bored and keyed for the larger shaft. However we're not sure if the existing hub is large enough for that diameter. The only data I've found on hubs is that, for medium load and shock, the diameter should be 1.85 x shaft diameter for cast iron. The heaviest application for this tire is 5220 in-lbs torque at 35 RPM, reversing, moderate shock. Can someone lead me to find design spec's. for this application?