inseam is not the critical dimension. your torso and arm length is more important, you need to compare the seat tube angles and top tube lengths of your present and the Cervelo and the type of bars and tri versus road position to determine. Given the cost of the bike I would suggest lots more research on your part.
Well I have done a lot of research. I rode a 54" and a 56". I felt like the 56" was perfect. Did not ride a 58. Purchased a 56. Told the LBS I did not want to pickup until today. He had to build it but did not want it until my birthday. When i got home I was thinking I should probably have tried the 58"
That was a week ago. When I called today to make sure it was ready to be picked up it turned out the bike was a 58". LBS ordered a 56" frame and that is what it was labeled. The LBS built it to my spec. Then noticed the frame was not the correct size. What a bummer.
So he offered to rush order a 56 frame and build it out. It will take a week. I told him to hold off and let me try the 58.
But I was then curious to what others that were 6' tall with a 35" inseam were riding in a P2C. Using google to do some searching it is pretty consistant that others with a similiar build are riding 56 not 58.
So I will give it a try tomorrow but I am thinking I will just have LBS reorder and build out the 56 and just have to wait.
get a fitting done..... i have the same inseam and ride a Argon18 E-112 in a size Medium, seems small yes, but very comfortable, more likely because of my torso or upper body length.. granted all bike makes will have different measurements, so all the more reason for a fitting. it took about an hour and a half to achieve a nice flat back aero posistion and to get comfy at the same time... well worth the time and money.
the fitting was a critical part of my purchase, its kind of like buying a car without sitting in it ... especially when your spending big coin on a bike...
Trek 1500 road bike, Giant Trinity Alliance tri bike
Agree with the others--go to a shop that can fit you and get fit.
That being said, if that's not an option (and it really should if you're going to spend $2500 or $3000 on a bike), it's easier to "make it work" with a bike that's half a size too small than with a bike that's half a size too big.