Although you wouldn't immediately think that less pressure on the truck
springs would make a car roll better ... further contemplation leads me
to believe that trucks that don't swivel/rock correctly will put pressure on
the wheel to rail contact point ... because even if the car isn't derailing
it is still attempting to climb the rails rather than following them.
I don't have a roll tester so I'm not able to actually test that - but it
makes sense (at least to my pea brain - *G*).
- Jim B.