I am upgrading my group set from Sora to 105 5700. I already have a sora crank with what I assume is a sora bottom bracket. I am about to purchase and install the 105 5700 crank, and I want to know if I should replace the bottom bracket to maybe dura ace for $33 or just leave the one already installed in there? The bike was bought new in 2010, so I know there is nothing wrong with it.
What do you think?