After the engine truck wheels, you might think the drivers would be an assured success. But I tell you, the first little blighter was harder to settle than my kids on Christmas Eve. No sooner would I push it into the cavity than it would edge back up and ask for another glass of water. There was no way to drug it or threaten it into bed. Finally, I had to start collapsing bubbles so I got it as far down as it would go and put the pressure on.
It was still not properly seated, and the result is a wheel that is about 25% too thick. I fought with myself briefly before deciding it is better not to compromise this early in the model. So, I guess we get to learn how to pull the urethane spokes out of a wheel now or make a new one.
Update: Nail polish remover makes relatively quick work of the urethane casting material. I let it soak for a couple of hours and most parts fell right off with a little gentle prying.
Pembroke:87 
Can you mount it in your lathe, and cut down the 25%?
Craig
Probably, but then the spokes will be too proud. No, the best solution is to pull the centre out of the wheel. Just have to figure out how! If worse gets to worst, I can just carve it out. It’s soaking in solvent right now while I cut the next set of spokes.
How tight is the fit of tire to center? Anything more than about .001” interference per inch of diameter tends to cause us engineers headaches in metal on metal joints…
The centre is cast into the tyre. I was aiming for a .02 mm interference for the axle, but overshot 3 out of 4 times. Even the one time, I’m not sure if I got it exactly as I may have been able to turn it; so I soldered it.