I was line turnaround tech on a Lufthansa 747 Combi for 2 years, weight is up near 800,000 lbs. About 5 times that space shuttle, it would max out so much going back to Frankfurt we would have to wait for temp drop around 10pm to take off sometimes during the summer. The tow bar is around 300 - 400 lbs itself. You would never bust it from a standstill with a truck, those photo ops are so rigged. I bet the tires are tremendously over inflated to cut the rolling resistance first. Stories, I got tons, nose gear sheared off, broken tow bars, upper lav dumps straight on someone's head, baggage carts blown over while still locked to cart train, blown wings lines shearing 100's of wires, digging birds out of engines, fried seagulls caught up in the brake packs as they taxied up ready to eat, bomb threats, mis fuels, wet start fireballs the size of a 2 car garage, off load mix up and nose gear rise about 6' off the ground.