What's happening to road frame shapes these days?

[AyeYo]

Is it just me or are road frames starting to look more and more like mountain bikes with massively sloped top tubes that are nearly a straight shot (same angle) right into the rapidly shriveling seat stays? The odd thing is that in most cases this seems (at least from eyeballing without comparing geometry numbers) to be done without effecting the actual riding position... so what's the advantage? The seat posts just keep getting longer and the head tubes just keep getting shorter to negate the top tube angle change. However, it does make for an increasingly large gap between top tube length and effective top tube length.



Back in the day, horizontal top tube on nearly all road bikes:




1998 Trek catalog, all remains horizonal




Here we go, 2005 Pilot brings the slight slope for some "endurance" geometry




My own bike, 2012 Z5. Similar to the Pilot, intended for endurance riding.



Now suddenly we've got this stuff...



This is a race bike? Looks like the relaxed rides of not too many years ago. In fact if you made use of that massive amount of steer tube above the stem it'd be MORE relaxed.



These are race bikes too? They look just like the Pilot. Solid rise from seat tube to head tube.









Cannondale isn't affraid. The CAAD10 is still looks like a road bike aside from those hideous discs.








What the hell is this a step through frame?



Same thing with this one. Go any futher and the downtube and top tube will be parallel and the seat tube won't exist.





I've seen that frame shape before, I just can't put my finger on where...

 

[danfoz]

Horizontal top tubes still make the best looking road bikes.

 

[Volnix]

I think it's supposed to be called "compact" geometry.

Also think that they use less material with that shape.

But I am very curious about the load case analysis on the frames.

Smaller triangles are not bad for strength though. Smaller (26) wheels are stronger then the 28's (all other things being equal) and that is probably why they are still used in MTBs.


What I don't like is that the front triangle is not a triangle, but some kind of trapezoidal shape. (Especially on the larger sized frames.) Maybe that's why there are so many failures in the headtube area, since triangles are a stronger shape.

But in order to create different sizes, whilst still being able to keep the "endurance" (higher handlebars), "race", "TT", or whatever fits and still use less material in the frame for weight saving the front triangle probably becomes a trapezoidal shape.

 

[AyeYo]

Less material is a really good point. Never thought of that one. There is quite a bit less material in one of these smooshed down frames than in a standard triangle frame. But like you said, the triangle came about due to strength, but the frames are getting less and less triangular. The bracing angles would seem to be weaker, but I'd be interesting in hearing what the engineers behind these frames have to say.

 

[Volnix]

Originally Posted by AyeYo
The bracing angles would seem to be weaker, but I'd be interesting in hearing what the engineers behind these frames have to say.

Me too... But I'm worried it's something like this:

 

[oldbobcat]

When critiquing contemporary bike geometry, it is important to distinguish between the seat tube going down and the head tube going up. These are two different phenomena here, for entirely different purposes.

My guess is Trek shortened seat tubes in their latest iteration of the Madone to compensate for the lack of a brake bridge.

The main rationale I'm hearing for compact now is that the longer seat post cushions the ride. And even the holy-grail brands like Pinarello and Colnago have embraced "semi-" compact.