I was at my local bike co-op last night and saw they had a wheel-set that had 29x2.1 written on tire, but on the rim on both sides said 650b. How is that possible? One of the co-op people said it's a 650b tire they are calling 29er, but is that even a thing? It was a front tire that had the disc brake already on. I was tempting to try it out on my bike build, but since sizing was questionable I did not.