I have also had problems with the center axle not rolling as well. As stated previously, the easiest solution is to just remove the center axle. As Nate said above, the bigger problem that I have had is the bolster pin holes being VERY poorly punched out. I also tried to fix this with the same result as Nate (the hole was punched poorly and when I tried to clean it out, the whole hole pretty much fell out and I had to use the other method of attaching the truck to the body).
For those who are concerned with prototypical accuracy, the following are the biggest flaws I've found with the cars: None of the Ringling cars have skirts, so they need to be removed on the coaches (not an easy task without messing up the lettering). The window patterns on the coaches are too uniform as the Ringling cars are former sleepers from various source railroads (almost all the cars on the real train are slightly different). These two problems don't bother me as much as the fact that all the sleepers on the Ringling train ride on 4 wheel, roller bearing trucks, not the 6 wheel heavyweight friction bearing trucks that are supplied. The only cars on the train that have 6 wheel trucks are the generator car and the animal cars.
All that being said, the flats, container car, and rack car (the show only used one rack car on each train) are nicely done. The artwork is pretty spot-on. Too bad you can't get that by itself to do more cars.
I wish MT would have included more of the small 20' containers as the flats were loaded full from end to end with very little space between them. Also, in the flat runner pack, I'm not sure what the heck the big hunk of plastic load is supposed to be (tent poles maybe....too bad they don't use tents anymore).
Nate