Some early production runs of 27"R FasTrack allow the wheel flanges to hit the molded plastic mounts that hold the rail. The worst engine I have is the newer Legacy PA/PA set. Its flanges even hit on the old SHS 30"R curves and will derail. I think fast angle wheels is a design unique to O gauge but not all the Lionel S gauge wheels are the same. I have never had a problem using SHS track with any Legacy steam engine or U33c, U36c, ES44 or SD70ACe diesel. Many of these engines will bump along on the Lionel FasTrack 27"R curves.
With the exception of the Legacy PA the issue is the track, not the wheels.