Quote Originally Posted by nscrbug View Post
As the title of my post states...I am wanting to swap out the FSA SLK carbon crank on my Cannondale Synapse for an Ultegra one. I have not been happy with the FSA crank from day 1, and I want it gone. I also believe that the big chainring on the FSA crank may be playing a role in the awful shifting problems I've been experiencing on the front ring. I know that I could just swap out the chainring itself, but at $120 for the big ring alone, I'd rather spend the extra $$$ and get the entire Ultegra crank. In addition to the Ultegra crank, it is my understanding that I will also need to replace the bottom bracket...as my current BB, an FSA BB30, is not compatible with the Ultegra crank. In speaking with a mechanic over the phone from Performance Bike, I was also told that I will need some kind of "adapter" because of the way the FSA bearings are in a sealed cartridge. This part has me a bit confused. Has anyone else here been in a similar situation, swapping out a different brand of crank for an Ultegra one? I'd be interested to hear what exactly was involved in the swap. I would not be doing the work myself, of course (have no clue on how to do it), but would like a good grasp on the parts involved. Thanks!

Linda
Hi Linda, good decision to ditch the FSA crank. They have a history of mediocre shifting. Nearly everyone who switches prefers Shimano.

The BB30 shell in your Cannondale is 42mm inside diameter, and the Shimano bottom bracket screws into threaded frames that are about 36mm inside diameter (and threaded). The adpter you need is LocTited into your frame and provides the threaded interior your Shimano bottom bracket cups need. Here's an image of one made by, ironically, FSA, along with the Shimano BB that threads into it:


http://www.labicicletta.com/edatcat/...SA-BB30ADAPTER
http://www.bikepartsplace.com/discou...-cups-italian/

Another option is an aftermarket bottom bracket that fits into your 42mm frame and whose bearings provide the 24mm inside diameter your Shimano crank needs, such as KCNC's:


http://fairwheelbikes.com/kcnc-bb30-adapter-p-2926.html
This replaces the Shimano thread in bottom bracket bearing cups, no need to buy them if you go this route.

A third option is to slip some Wheels Manufacturing shims into your frame's existing cartridge bearings. THey step down the 30mm bearings to 24mm to fit your Shimano crank.

http://www.competitivecyclist.com/pr...9081.19.1.html
These are a little different; they load your crank's axle slightly differently than Shimano intended and are said to shorten the fatigue life of the axle. Nevertheless lots of people use them. No idea how long we'll have to wait to see the rash of breaking crank axles. Maybe never?!? I'd use them if they were convenient.

Hope this helps!