Originally Posted by
alexk_il
No idea. How do I tell?
My jerk knee reaction is just to replace the BB. Is it not going to help? The BB is a threaded one with what seems to require a Hollowtech spanner.
Slip the crank spindle individually into each existing BB bearing, but not through both. That will tell you if you have a single or double overly "tight" bearing in the old BB.
A new BB will help if it's a question of having an overly tight bearing in the old BB (e.g., one with a slightly undersized ID for the new spindle's OD). However, if the bottom bracket shell ends (faces) on your bike are not exactly parallel, the bearing bores on both cranksets (new and old) may not line up exactly - and the fit may also be tight when you try to pass the crank through the second bearing. In that case a new BB may not help much if at all.
Assuming your frame is metal, having the bottom bracket faced by a bike shop with the equipment and skills to do that would ensure the shell faces are parallel. But not all LBS do that any more.
If your frame is carbon, dunno what to tell you. Don't think facing one of those is a good idea, even if it's possible.