biker7 said:
beg to differ back at you lokstah. Its a simple geometry lesson. One could argue comparing same size frames both the seat tube and sloped top tube are shorter for the same sized compact frame hence lower weight. The shorter seat tube of a compact frame is partially but not completely negated by the added weight of the longer seat post but the shorter length of the sloped top tube which creates the same virtual horizontal top tube length of a convention frame from seat tube to steerer tube is not to be denied. Always was and always will be shorter than a level top tubed conventional frame and hence the weight savings.
George
Triple differ ya.
First off, notice that it's impossible to discuss this without bringing in faith-based suggestions, such as compact lightness being
"partially but not completely negated by the added weight of the longer seat post." You're wading into massive variables territory here, George. It depends on the seattube height (many supposedly compact frames have tall ones). It depends on the seatpost itself (is the seattube low enough that a comparatively bulky seatpost is required to counter the long extension?). Is the distance between the toptube-seatstay junction and the saddle cutting into stiffness? What frame are we talking about here, anyways? An Airborne Torch? A Specialized Allez Pro? A Giant TCR? A Lemond Tourmalet?
All pointing, of course, to
my point that you can't
make secure claims about compact geometry benefits--nothing that's meaningful beyond raw, pre-production theory, at least.
I'd also disagree with the suggestion that a sloping toptube necessarily involves less tubing than a classic frame sized for the same rider.
Assuming a standard seattube angle, you're looking at a negligible difference only, which may or may not be countered by a difference in the seatstay angle and junction placement. Depending on the angle of the slope and the angle of the seattube, though, you're bound to have instances where the geometry doesn't favor either.
All in all, it's a wash across the board. I've got a 2002 alloy TCR (quite compact) and a 2004 Klein Q-Pro (classic and long), and the latter is both stiffer and lighter. I wouldn't chalk that up to classic versus compact geometry, though; it's just a better frame.