When first installed (with factory correct preload) on my DT Swiss 370 tee hub these bearings were some of the smoothest rolling bearings I’ve ever rolled on. After approximately 50 miles of smooth tarmac riding they have developed a severe click and a catch in the overall smoothness- nearly as bad as the original bearings they replaced which had approximately 5-6000 miles ridden on various road surfaces. They were replaced at the same time as the free hub by a professional bicycle mechanic using proper extraction and installation tools, so incorrect installation procedures did not cause this problem. When I returned to him to diagnose the problem he indicted some sort of coating on the balls was flaking away. I’m dissatisfied overall because of this.
Bought these to replace a set of bearing in a rear Dt Swiss 350 hub that had rusted from water leaking into the seals. These bearing are the best investment I have ever experienced with improved ride quality and rolling resistance, next to a new set of tires. Will be upgrading the front bearings immediately.