>BART discovered cylindrical wheels in 2018. ... uhh, your own link says otherwise, emphasis mine... >To answer the question, the original BART wheel profile,

>BART discovered cylindrical wheels in 2018. ... uhh, your own link says otherwise, emphasis mine... >To answer the question, the original BART wheel profile, you can consider it like a cylindrical section of pipe. While the new profile is tapered, like a curved barrel, if you could imagine that the cylinder shape pipe rolling down a slight incline it really just wants to go straight. It doesn’t want to turn to the left, it doesn’t want to turn to the right, it just wants to go straight. That’s what our original BART wheel is like. Whenever it would come to a turn the wheel flange is what makes that wheel turn and go around the curve and that results in a lot of extra wear. The new wheel shape that we call the BT-3 Wheel Profile tends to want to self-center between the rails and it even steers in the turns so the result is much less wear and noticeably less noise.