Pro tip for installing SRAM cranks: Install them twice. When you crank down on the non-drive side bolt that holds the crank together, small amounts of material will come off the threads (I mean incredibly small amounts. You won't be able to see it). Unscrew the crank arm, and reinstall it so that everything fits nicely. My race mechanic buddy has noticed Rival cranks coming off/loosening up on their own in the past. This is the solution.