A recent video from GCN show this spring effect that some people on steel frame suggest:
In relation, the work of Jan Heine and his blind test with 4 steel frames: https://janheine.wordpress.com/2018/01/ ... re-faster/
https://janheine.wordpress.com/2011/02/ ... stiffness/Jan Heine wrote: I hypothesized that relatively flexible frames were easier to pedal, because they did not resist our pedal strokes. We could get in sync with the frame, pushing down harder during the power stroke. The frame stored the excess energy as it flexed, and returned it to the drivetrain during the “dead spots” at the top and bottom of the stroke.
https://janheine.wordpress.com/2011/10/ ... stiffness/