I just purchased a TCR1 composite size large.I bought this off e-bay.I had my previous ride for 12 yrs.So I know the change is throwing me off a bit.While I think I will like this bike I should have paid more attention to Giants sizing.I am having a huge problem getting this bike to be comfortable.I,m 5'10.5" and I bought a size large..so I,m not too far off the mark,but it still is frustrating trying to get this bike to feel "right" to me.I have the stem "flipped" but I think I am going to go with a shorter stem.I also replaced the #2 aero post with just a regular giant carbon post.My next step is replacing the crank set with either a 170 or 172mm FSA carbon.The present set is 175mm ultegra.My biggest question??Is there a way to tell if my bb is octalink or ISIS without taking it apart?? Also does anyone have a suggestion for a good qaulity comfortable seat as I find the stock seat does chaffe me a bit.
Thanks.

If the crankset is Ultegra, you can be certain the bottom bracket is not ISIS...

Ok.Thanks for the info.The crankset is Ultegra so it must be octalink then.Thanks for the help.