What is the difference between a properly sized aero race bike, with the saddle pegged 5″ above the handle bars and a standard round tube race bike with the saddle only 2-1/2″ above the bars?

Make it interesting and add skin tight racing kit opposed to a looser fitting jersey.

Everything else comparable… Aero racing wheels, road racing helmet, etc.

Last year, on a special 3/4 mile descent I managed a max speed of 43 mph on my old Trek 5200.

On my comparably equipped Specialized Venge, 53 the first time and 56 mph the next two – on the exact same hill.

Now, this isn’t to say it’s all in the bike because I had big gains in the setup, the lower handlebar and the tighter clothing.  In other words, the aerodynamics were much improved…

I was a follower when it came to how I should set it up. I took the advice of virtually everyone who said an upright setup is more comfortable, so when I brought my Trek home from the shop, I rode it as it was set for a while.

Over time I started working the handlebar down but once I got to 3-1/2″, riding in the drops became less than comfortable. I still went so far as to devote one ride a week to just riding in the drops so I could try to get used to it.

Eventually I got that down to 3-3/4″ or so but that was about as low as I could comfortably go.  Then I bought my Venge, the frame is smaller by 2cm with a sloped top tube and shallower drop bar… With the shallow drop handlebar I was able to lower the top of the bar far beyond that of the 5200 (5-1/4″).  Also, the difference in geometry between the standard flat top tube and the sloped meant added comfort – and this one is hard to quantify scientifically, the Venge just feels better, even with the lower bar.

The standards have me, a 6′ tall male, on a 59 cm frame.

This:

VS.

This:

And this:

(This was after one serious climbing effort – I was completely gassed)
VS.

This:

13 mph, coasting…