Dean- The priorities that a large manufacturer has are different then those of a small/custom builder. A major one is to lower the cost of production. (Think of all those companies that seem to spend more on marketing then product...) Sharing tooling between different models or in this case, frame size runs, is an early cost savings area. I have heard of a number of companies that use the same seat tube angle, head angle and or top tube length between various sizes. This produces a larger frame with too short a top tube and, often, too little seat set back. A small frame suffers the opposite. With both having handling that's a compromise. AS the buying public gets more savvy the product designers get more detailed. And at some point the marketing value of specific geometry for each size out weighs the added cost to make the fixtures. These days with a form needed for each size (as often with OT carbon manufacturing) the added cost to design specific geometry is not really any more. Andy.
> List (and especially framebuilders),
> I have a related question, and forgive my ignorance but...
> Was there a shift in frame-building philosopy/technique so that more
> large frames tend to be built with longer (and proportional) top tubes
> they were back in the day?
> My original race bike from 1972 is Falcon San Remo that fits me well at
> Like a number of frames from that period, although it is fairly large
> (24/24.5 c-t-c) it has a fairly short top tube (22.5 c-t-c) which works
> for me, since I am more legs than arms.
> These proportions seem to be true of others from the period as well (as I
> have recently been reminded in an off-list exchange), ie. the larger
> tended to have extended seat tubes once they hit the upper end of the size
> range without a proportionate increase in TT length.
> Coming back to the sport, I was surprised to find more large frames that
> were proportional (often "square") so that I now ride a nominally smaller
> frame to have the same reach that I had on my original bike. Fitting on my
> orginal bike gives me the "fistful of seatpost" that was deemed correct
> the time; fitting on my newer (~off-topic) Simonetti gives me more
> [FWIW, I am indifferent to the issue of standover height since I don't
> over my bicycle. :>) ]
> The resulting loss is something that, if not a "better" ride, was
> a different feeling on the bike.
> Dean Kernan
> Pomona, New York