I wondered, how would this work with an axle-less low-floor bogie? The answer I found here[1] is — it doesn't. “… there is only a single series of trams that have these bogies, later versions returned to the traditional type with axles. … The wear problem is because those bogies don't seem to track as well, they go from left to right in the track”. The implication is that there were people designing rail vehicles who didn't know how they stay on the track.
There are more trams with axle-less bogies now.[1] The goal is to lower the floor height, eliminate steps, and improve wheelchair accessibility. It gets complicated. Some systems use big driven wheels and small trailing wheels. Some have a geared axle between the wheels. Siemens has a system with motors on each wheel, with the wheels locked together electronically. AEG tried something like that, with less success. Speeds of the more elaborate systems are rather low, below 70km/h (44mph). That appears to be a limit of the axle-less design.
[1] http://modeleng.proboards.com/thread/4521/chilled-iron-tram-...