Originally Posted by GhostRider62

The 1 watt advantage was at 250 watts for a crappy bushing pulley. Less than 0.1 watts against steel bearing pulleys like Hawk. Around 0.3 watts against most pulleys like Dura Ace or Sram. Approximate numbers by memory. I would not be surprised if that huge OSP pulley costs 1-2 watts to the air at 40 kph.

The one claim that CS makes that contradicts other research is lower friction due to slacker chain tension. They claim 1-2 watt advantage due to lower chain tension IIRC. I'm not an ME, but having looked at it a few year ago, I came to the conclusion their claims were BS. If it was 2-3 watts, I would spend the money to be honest. I came to the conclusion that 80 dollar Hawk bearings were just fine when the stock SRAM pulleys wore out.

I wonder if there is a 5 year old British ME who has looked at these claims?