In a message dated 6/22/2004 11:46:07 AM Eastern Daylight Time, tullio@TheRamp.net writes:
<< The "science" also says that the rear triangle is an inherently stiff triangulated structure. The reason that small diameter, thin-walled stays can be used is that the geometry provides the necessary strength. The front triangle is not triangulated in three dimensions. So, it requires much larger diameter tubing to have sufficient lateral and torsional stiffness. >>
Not sure about the science but my 30 + years of building/selling experience and observation are that larger & thicker wall seat stays lead to stiffness and resistance to flex (same thing.) Smaller diameter stays are flexier and springy. Yes, the rear end if a bike is a triangle and the stays are in compression when a direct vertical load are on them, but a bicycle frame is a more dynamic structure and gets all kinds of twisting loads beyond just simple vertical ones. So, in mid range to small bikes, comfort and resilience can be gained from 1/2" or less seat stays. Big riders (heavy and/or tall) benefit from 9/16" stays or more. Sprint bikes, tandems etc. can have BIG stays.
IMO, the pencil stays could be OK, even desirable for all who want ride-all-day frames and who are not too heavy or tall.