Originally Posted by
Kontact
Everyone went to those low, boxy type of stays like the Merida or S-Works because of aerodynamics. The shape is good for air flow around the seat tube, and they are the lowest height that is UCI legal (otherwise CF aero bikes would have no seat stays).
The other shapes are largely designed to look comfortable or cool. But it is true that if you want the chainstays to flex but not be paper thin, small diameters work best.
Yeah, I understood dropped seatstays to be an aero thing.
In your second paragraph, I don’t know if you meant to change to chainstays, but you’re absolutely on point that it’s the chainstays which provide bump compliance. Seatstays are largely a vestige of a bygone era, and not necessary elements with modern materials. Back in the ‘80s, Trimble was making seatstay-less frames, and Trek’s Y-Foil in the ‘90s was very successful seatstsy-less design. Cervelo’s P5X from around ‘16 is a more recent example.
Those are carbon fiber, but looking at English Cycles steel designs with their literally pencil-thin seatstays, on frames meant for crit racing, not comfort— and you have to wonder if the seatstays don’t inhibit bump compliance rather than provide it.