From the
instructable site: "
Tip: The locknuts should not be too tight. All they need to do is to make sure the cone nuts don't slide. Screwing them on too tight will push the cone nuts in toward the bearings. This allows the biker to adjust the tightness of the cones without having to disassembling the hub. Cone wrenches cost around $10. Personally, I believe they are unnecessary." Eureka: I've found my problem, sliding cone nuts!