Is this a thread from the 90's that's been revived?

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2010 Guerciotti Whisper
2007 Bianchi 928L (update Sep '11)
1999 Bianchi MegaPro 25CrMo4

I thought the OP was referring to the sloping tt of some bikes seem to be getting steeper.
The new Giants appear to be steeper. The problem is they look OK in the smaller sizes whereas the bigger models look like kids bikes. Bigger frames look much better with a more gradual slope.

I also think the sloping top tubes make it easier to fit bikes to less athletic riders. With a sloping tube the height of the bars in relationship to the seat are generally higher, creating a more relaxed fit without resorting to high rise stems or a large stack of washers under the stem on a long steerer tube. The tall head tube of my 54 cm Orbea (53.5 top tube) places the bars much higher than the small head tube of my 49 cm Ciocc (52.5 top tube), even with the stem of my Orbea slammed and my Cinelli as high as it can reach. Yes, the Orbea is a slightly larger size, but the bar is 4-5 cm higher.

Just my two cents...

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1984 Ciocc Aquila 84 - SLX frame and full Campy Super Record
2006 Orbea Lobular - Aluminum and Carbon frame with Ultegra

You can swing your 'nads over more easily if the top tube is lower.

a sloping "compact" geometry bike does not necessarily have a taller head tube. the two features are mutually exclusive.
the general benefit of a sloping top tube is that it takes standover height completely out of the fit equation. with traditional geometry bikes, if someone comes in with proportionally short legs and long torso, the ideal "reach" of bike will be too tall for him. there would be no standover clearance. if that person went down in size, the reach of the bike would be too short. a sloping top tube addresses that very well.
i definitely think giant got it very wrong in the beginning. specialized did it well, cannondale with their 2cm top tube drop is a nice middle ground.
as for lateral/torsional stiffness, overall i dont think it makes too much of a difference one way or the other, but i do believe it's easier to build in vertical compliance for a given lateral stiffness, especially with seatpost flex.

For old welded, fillet-brazed and otherwise put together from pieces of tubing
frames it didn't matter but for carbon it make sense to have a continuous
undisturbed strand of fiber from TT to seatstays - is that the reason too?

Anyway, I hate short top tubes and tall head tubes that came with this fashion
and people are using spacers, up-sloping stems and non-offset seatposts
along with already relax geometry. Heresy.

I think for larger sloping geometry frames the headtubes are in fact shorter than those found on traditional geometry ones. Even on an ultra `relaxed' fit Specialized Secteur in size XL I can set it up with a saddle/handlebar drop of 10cms just by removing the spacers, I could get to 12cms+ with a change of stem. So maybe the long headtube issue is only found on the smaller frames?

stack height is not affected by sloping tope tube, if its longer or shorter its because they wanted to make it that way not because they had to beacuse of the sloping TT.

sloping may or may not be stiffer but because of the longer seat tube needed it make the whole package more flexiable, long eat tubes especially 'aero' ones flex alot

As you can see, nobody knows WTF the original poster is talking about. It's like asking, "What's up with bikes these days?"

All I'm asking is whether there was a functional reason for the sloping geometry on the new road bikes, or whether it was just an aesthetic move. In my opinion, my question was answered.

Not functional. Not aesthetic. Strictly business. Fewer frame sizes to fit more people. Less costs of manufacturing. More profits.

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My Colnago C59
My Special Colnago EPQ

I have a slightly sloping top tube on my custom frame (2degrees). My reason was simply to have enough seat post showing so I could clamp it in the bike stand. Works for me.

GT had that rear triangle thing going on some years back. It had the seat stays attached lower on the seat tube and was marketed as giving a stiffer rear triangle. All they needed to do was slope the top tube. Giant has often said that sloping top tubes came about to reduce the number of molds to three, small, medium and large. Some riders like to squat on the sloping top tube to get more aero.

It has become a trademark for comfort fit bikes as it hides the really long head tube you would otherwise see. Look at the saddle vs stem hight. Many of these bikes have the bars almost level with the seat. Lets you "look" faster

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WW Velocipedist Gargantuan

For a guy that rides a 50cm bike sloping is always welcome at 5'5"

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Let's finish the ride with a 20% grade.
2011 Scott Addict R1 Matt black
2012 Cannondale EVO "Storm Trooper" white and black