How have you validated the claim of 4 Watts saved at 70 rpm? Seems like a lot to me!
Well, of course I have a Powermeter but I have not established a protocol that would have any scientific value.
However, the feelings with these bearings and the standard Rotor 41/30 bearings are so different that the gain is significant, a few watts, not a few 0.1W, because I cannot feel a difference of 0.5W, whereas 2-5W, yes !
I have read different friction revues and tests. They say that the gain is between 0 and 5 watts with a BB ceramic upgrade.
I have also tested a wide range of BB in both steel and ceramic, and of course different ceramic brands. All brands don't have the same quality. Chinese ceramic bearings are often a nightmare for customers, giving and horrible image of ceramic products, whereas there are small brands like cyclinceramic who are passionate by high end quality products instead of doing volumes in China.
So, my conclusion is that a Rotor BB41/30 steel is among the worst steel bearings, and the BB41/30 here http://www.velo-perso.com/en/bb86-frame ... rings.html
is among the smoothest ceramic bearings that money can buy.
Therefore, the gain must be on the top of watts savings and 4W at 70RPM make sense because we compare a bad BB with one of the finest.
I'd be glad to refund any order if customer would not be fully satisfied of this product after a few rides.
This product is changing my view on Rotor 30mm products, because upon today, Rotor bearings 41/30 are so bad that they cancel all the advantage of owning a 3D+ or inpower cranks... and I have been using a 3d24 instead in order to get better overall performances on the combo crank + bearings, because there are several 41/24 bearings already available from various brands and with a good quality.