> The smaller wheels in front are there to prevent that by guiding the locomotive into bends. I think, in the US these are also known as "pilot wheels" for tha

> The smaller wheels in front are there to prevent that by guiding the locomotive into bends. I think, in the US these are also known as "pilot wheels" for that purpose. The need for them (or the use you get out of them) also depends on track quality. If you run on lightly built track, the improvement is significant. (Mind that track isn't fixed to the ground, it rather floats in the ballast, the stones in which the track is embedded. The built quality of the entire assembly has implications for stability and the kinds of speeds you can run on that track, especially with heavier locomotives.)