Wow John. Of course if the loco didn't have four (4) rubber tires the wheels would spin a little when it was overloaded, so you would never see that kind of current draw in real life. For years, a cardinal rule of locomotive building and re-powering is that you don't weight a loco so heavily that the wheels can't spin when it's overloaded. Add rubber tires, especially four of them, and who knows! With gearing that low, the wheels might spin even with the tires. But the current draw will be higher than it would with just two, or no tires at all.