> So why did BART go to cylindrical tread? Was there a hunting or other problem with the
> initial batch of conical treads?


I seem to recall someone in the shops explaining to me at the time, that Bechtel had decided that the gentle pitching and nosing of the cars was unpleasant. Someone else (at PBTB) explained that the rather rigid "inside frame" trucks could not be tuned and dampened effectively, due to the narrowness of the frame. So they instead chose to tighten the gauge tolerances on the flanges and run with cylindrical wheels.

Personally, I found the ride of the first cars to be no different than any other rail passenger car. So I never really bought into the first theory. The second theory, in my mind suggests a very poor truck design to start with.

So who really knows for sure why they did this, rather than actually produce a truck design that worked. Probably because the first articles were already delivered and the cost of a redesign at that point would have been high - and all on the design consultant - Bechtel. Less expensive to just bullshit the customer and move on.

BART had little or no engineering expertise on its payroll at that time that could look out for its interests; hence it was easy prey to any contractor with its own agenda. As for me, I tend to think that since Bechtel had little experience building railways, they just plain did not know what the hell they were doing! Any more than BART did!