I usually do a 15 mile route that includes streets and curbs, bike trails, a little dirt, and some very rough roads.

The guy at the LBS told me they might be metric and they might be meant for 37 x 597 tires instead of the American standard 37 x 590 tires (26")
I have some of those gum wall 37 x 597 R7 tires, meant for old Schwinns. I'm wondering if those would work. I tried them once on a 26" rim and they wouldn't stay on the rim. Maybe this rim is a different size.
Guess I could try it and be real careful. Making sure the tire doesn't blow off the rim while inflating or come off while I'm riding.