I have a carbon Cannondale mountain bike with what appears to be a PF30 or PF30A bottom bracket: two 6806 bearings pressed into cups, which are pressed in turn into the frame.
With the bearings and cups still in the frame, the NDS bearing feels slightly gritty and the DS bearing feels very gritty with high initial friction. So I'm thinking I need to replace one or both.
Except when I pull the DS bearing (comes out with the cup), it feels fine. Maybe 90% of ideal, no obvious grit even under pressure. Press the cup and bearing back into frame, though, and then it feels terrible again.
I assuming this is a frame tolerance issue: it's squeezing the bearing too much. If so, then replacing the bearing won't get me anywhere.
Does this sound like the right conclusion? The frame is still under the factory warranty.