Tires have been slipping and falling off.
On a close look the side rod between each drive wheel there are no nuts to unscrew looks likes pins pushed in but they will not come out??
How do you get the side rods off to change the tractions tires??
The instructions in the MTH manual for the engine say;
"Traction Tire Replacement Instructions
1. Remove the side rods from the wheels in order to slip the new tire over the
grooved drive wheel. Make sure to note the position of all rods before removing."