I am a roadie and ride a Cervelo R3 but just for a change of pace, I bought a Cervelo P2 SL this fall. Whenever I ride the tri bike, I can tell that I am straining my quad muscles much more than on the road bike. I think I am fit properly and the bike feels comfortable. My power output on my powertap seems similair on both bikes. Of course, my hip angle is somewhat less on the tri bike.
Is it normal to use the quad muscles more (and maybe the hamstrings less) on a tri bike? It is hard for me to picture why this would be the case but my sore front legs confirm it.