Aerodynamics are vital in cycling, especially for time trial specialists and triathletes. Because of the impact of air resistance on their speed, these athletes build their TT-bikes with the design focused on aerodynamic issues. Therefore, special „closed" tt-chainrings are becoming more and more common, and many suppliers have them in their product portfolio.

If you put closed chainrings on your SRM PowerMeter, please be aware that the slope might change. Even if you set your the offset at the beginning of your training session, the power data might be incorrect. Please send your PowerMeter to SRM for calibration with the chainrings attached. Then you can be sure that your power data is accurate, that your training zones fit your individual training program, and that you can ride to your predicted pacing strategy in competition.