Originally Posted by
Qioxz
I heard that Carbon is stiffer than aluminium? So my thoughts were that Carbon rides less smooth on a rough surface..
Well beside that, you think The difference between aluminium and carbon is worth the prize more than the difference between 105 and ultegra?
Because aluminium has no fatigue limit, aluminium tubing for bicycle frames has to be very stiff. Carbon (or steel, or titanium) frames can be made as stiff as those from aluminium, but as a general rule they will be a little springier and an aluminium frame will be the stiffest.
That doesn't necessarily mean an aluminium frame will be the less comfortable ride, though. There are a lot of other factors besides frame material that contribute to comfort. And as mentioned above, many aluminium frames will be matched with carbon forks to take some of the road "buzz" out of the equation.
As far as ultegra vs 105 is concerned, how many ways do you want the question answered? In my view, Ultergra isn't sufficiently superior to be worth the extra. But others will have a different view. I'd settle on the frame you like best, and go from there.