does anyone use grooved bearings for competition? I would imagine it would be hard
Man... people REALLY overestimate the importance of these things.
If I give you a yoyo with a grooved, curved, or grooved and curved bearing and you don't sneak a peek into the gap, I promise you that you will not know what bearing I put in there. All these differences people imagine are just that... the product of imagination. The only thing that a grooved and/or curved bearing will do is center the string on the initial throw. As soon as you start adding layers, the "loop" of the string pops out of the groove or is pushed out of the center of the curve. It doesn't stick there, defying all laws of physics, and halve your available bearing. There is SOME friction in the middle of string-on-string compared to flat... but strings actually slide very easily along one-another. Much more easily than they slide against a response pad, for example....