I have read before that the Rival bottom bracket does offer some friction. I can't remember where, but I just checked BikeRadar and pulled out this quote, "The bottom bracket is really the only letdown here as the GXP design continues to run with more friction than we would prefer. Thankfully, smoother-running aftermarket upgrades are readily available."

Here's the full review on 09 Rival http://www.bikeradar.com/gear/catego...rival-09-33871