To the proponents of TT bikes being so superior. Spend some time on SlowTwitch - with TT pros, industry engineers and others that live aero.
You will soon learn that for all the hype, the best bike will gain you some time, but not nearly enough to make up for a poor engine.
I stand by my minute thirty over 40km as a decent estimate. Your experience of 1.5mph faster on your Speed Concept is not far off.
I ride a P4 with a disk. I also ride an S2 with good position. The difference is not huge.
Let's not forget as well that pro riders spend most of their time drafting. This erases the aero benefit of the super bikes - again, an old school alu bike that I can get on craigslist for 1200 bucks would be in the ballpark (with tire upgrades). Sure weight matters in climbs over 12%, but again, a pro-level rider will crush the rest of us on a 20 pound steel bike (that is heavy), no matter what.
Overall, the point is that there is a myth among many non-cyclists that "if only I had a good bike, I would be really fast too".
This is like when your co-workers believe that if they tried really hard, they could run a 2:20 marathon.
Read Lance's War for the anecdote on Floyd Landis - as a kid he rode a piece of crap in track pants every night. As soon as he started racing it was obvious that he was world class - even as a teen. He did not need a fancy bike to become world class. Not even close.
I will easily admit that if you want to become a time trial specialist, and you are currently losing your 40km time trials by up to four minutes, you should have a dedicated TT bike. But, to the cyclists out there, a 2008 P2 with a wheel builder wheel cover, some latex tubes, and a used aero helmet, can be had, all in, for about 1200. That is a small price to pay for being a TT champ isnt it?
Second, if you have any promise at all - you will get gear comp'ed.
So let's all please stop the whining about how cyclists are only fast because they spend money.