Originally Posted by
jrobe
I will guess that the modern TT bike will have a 30-60 second advantage in a 1 hour timetrial (just a guess).
I did a 20 mile time trial in the last week on both my Cervelo R3 road bike ($4000 or so) and my Cervelo P2-SL aluminum TT bike ($1500, cheap standard wheels). I went over 3 minutes faster on the TT bike. In a side-by-race, the TT bike would have been over a mile ahead.
TT bikes are crazy fast but, obviously, the main advantage is in the aero riding position and not the bike. The interesting thing is that I ride both bikes in almost the same riding position (very similiar hips angle). I am just rotated more forward on the TT bike because of the different geometry. Both are quite comfortable.
Similar results here. I'm sure a wind tunnel tested aero CF TT bike is marginally faster than an older round tube steel TT bike, but the biggest change is position. My faster 40K ever was on a bike similar to that pictured although I had much more aero Syntace C2 bars and base bar and Nimble tri spokes. I've come close to that time on my P2C, but never matched it. Of course the state TT course isn't as fast since the location has changed, so I'm not sure how much is bike vs. totally flat course. TT times are really only comparable on the day and course that they happened and sometimes not even then.
PT reading have me at 21 on a road bike and 23 on a TT bike for the same power (280w) on a training rides. I've never ridden a road bike on a real 40K with power measurement, so I don't know the difference at 25+ but I would imagine it would still be a 2ish mph difference. The steel TT bike would probable be a 1/2 mph slower than the P2C.