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Discussion Starter · #1 ·
Are the new external bearing cranks more finicky to install then the traditional style ones? Also, is not having a parallel BB more of a problem with them than a traditional set up?

Here is my problem. I recently got a new frame and set it up with a FSA mega exo system. Upon installation the bearings felt tight and the cranks will only spin about 2 revolutions with a slight push. I checked my Ultegra cranks on my other bike and they spin 4 1/2 revolutions with the same effort. The FSA's have about 800 miles on them and the Ultegra's have about 8500.
 

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The external bearing crankset systems do use the frame shell faces as reference. The cups tighten on the shell surface, and non-parallel surfaces will mean one bearing is not running square to its mate. However, it the shell must be off quite a bit for this to happen. The previous version of cartridge bearings tightened in the shell, but the left and right set of bearings did not rely on the shell faces for alignment to one another.

Contact FSA, they are good with customer support.

See also on external bearings
http://www.parktool.com/repair/readhowto.asp?id=95
and for facing
http://www.parktool.com/repair/readhowto.asp?id=97
 

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Friction diagnosis

hank scorpio said:
Upon installation the bearings felt tight and the cranks will only spin about 2 revolutions with a slight push. I checked my Ultegra cranks on my other bike and they spin 4 1/2 revolutions with the same effort.
The key question is whether you feel any binding or roughness as you turn the BB axle. The friction difference you are seeing could easily be, and most likely is, just the friction of the contact seals and new grease in the new cranks vs. the old ones. If the axle turns smoothly, then the amount of friction you are "seeing" will have no significant impact on your ability to deliver power to the rear wheel.
 

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The new BB designs won't tolerate a shell that is much narrower than it ought to be. Whereas in eternity past, it was desireable to face the shell, doing so with the newer designs, unless it's grossly off, can lead to a frame that won't be wide enough to tighten down cranks. Bottomline, unless it's really bad (and this is rare even with factory frames like Trek or Spec), don't face the bottom bracket shell. It sounds like everything is fine, though.
 

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Discussion Starter · #5 ·
Thanks for the replies!

I took the system apart again today to try and see if there was any markings resulting from friction or some other obstruction. There wasn't but it led me to another question specific to the Mega Exo system. There were two tube type spacers between the bearing cups. I was thinking that the inner tube spacer might be only for shipping purposes and is to be discarded once the crank is installed. I emailed FSA with the same question but I haven't heard anything from them yet. I know they very helpful because this crank is actually a warranty replacement from them of an older crank. I also looked at their installation instructions that the have on their site and there is no mention of the inner spacer, only the outer one. This extra spacer may be the cause of the friction I am feeling in the cranks.
 
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