OK, so I have researched this to death to no avail. Many have asked the question, but no one ever answers it....

I have a 2011 Spec. Roubaix Elite Apex, which utilizes a Truvativ Power Spline bottom bracket. In the near future, I would like to upgrade the gruppo to SRAM Rival, which will require a new (different) bottom bracket. The bottom bracket shell on the frame has a faced surface on only one side (the chain side). The other side is threaded, but no face. For the power spline BB, no face is needed on that side.

My question is, what bottom bracket can I get to accept the SRAM Rival Crankset? There is a thread on RoadBikeReview called "Apex to Red crankset upgrade questions" where a guy put on a SRAM GXP with external bearings (on the same frame as I have, it turns out), however this doesn't seem right because the non-chain side of the bracket shell has no face. What is he gronking that bearing against? On my bike, the bearing would be grinding right up against the carbon.

I am hoping that this thread doesn't turn into a power spline hate session, we already know it is heavy and that it isn't the best design. What I ask is that someone tell me what the correct BB is to use when upgrading this particular set-up to SRAM Rival, maybe address my concern about the lack of a faced surface on the left-hand side.

Thanks Loads!!