Originally Posted by
Nessism
The heat treating does not affect stiffness. That's a misnomer that's been carrying on for decades; back to the 753 days at least.
It's my understanding that the most important tube in the front triangle is the down tube. My first frame used a long butt .8/.6 down tube and it was considerably stiffer than my subsequent builds using shorter butt .8/.5 tubing.
If the frame is taken as a seperate from the rest of the bike device then I agree that the DT is the member which most determines torsional (pedaling loads) stiffness. But the frame is not ridden without other elements that add their flex. I've learned that the fork's steerer contributes a lot to the overall feel of a bikes stiffness. Also the more the load is over the rear wheel (like panniers or rack top stuff) the more the top tube comes into play. Andy