The #8210 has no "pewter" anything on the wheels. In fact, there are no tires on the wheels. They are simply sintered iron, single piece wheels. The outside pair have flanges, the inside wheels are flange-less. Not only should the 8210 easily negotiate O-31 curves and switches, but it will also negotiate O-27 curves and switches.
Sounds like you may have binding somewhere in your valve gear. Pick up your engine and flip it over. Do the wheels roll freely by hand? No hang-ups? They should. Trouble spots to look for: the smoke unit lever can be jamming. The eccentric crank can be in the wrong position.
Jon 
