Whatever other advantages you can cite, if you can find a set of trucks with wheels that aren't tapered and one that has wheels that are, but are otherwise the same (same bearings, same wheel diameter, same wheelbase), and you test them you discover:
- they roll with the same amount of friction, etc., on straight track, whether tubular or solid, at least to the limits of what tests I could do which were probably accurate to only 10% or so
- the fast angle wheels roll with least friction on tubular curves - about 20% less on 36 inch curves.
- the fast angle wheels roll with just about the same friction, maybe a tiny bit less but not a lot less - in curves on solid, flat-top track.
Thus, I always assumed they were invented mostly to reduce the very evident slow down on O-27 curves you sometimes get with toy trains.
