My training friend and I were arguing that top tubes should be about the same length on road and tri bikes. I disagree. I like small frames with lots of stem and seatpost showing.
My road bike has a 55.5cm top tube with a 12 cm stem. 73 seat angle. Mt TT bike on the other hand has a 54cm tt with a 8cm stem. 76 seat tube angle. Both fit extremely well and are extremely comfy.
How do others road/TT bike top tubes and stem length compare?
Comparing a tri and road bike, depending upon the manufacturer and frame size, if you take one of each in your size the top tube is usually 2-5 cm shorter on the steep angle bike. One of Slowman’s beefs was how some early tri bike manufacturers didn’t decrease the top tubes accordingly, nor shorten the head tubes for that matter.
To settle the arguement with your friend go to the Cervelo site and compare the geometries of P2k/P3 in the 75 and 78 degree charts. For example, the 54 cm model has an effective top tube 2.5 cm shorter at 78 degrees than at 75.