I've seen very occasional posts where they needed to be re-torqued on a new unit after a bit of use or service, but I think that is standard operating procedure on all tractors. I don't recall seeing anything about the Kubotas having a problem with the lug bolts loosening though. Closest thing that I recall is some older style hubs coming loose from the axle on some older models that had the option of changing the tire width...if i remember right, that was a pretty easy fix, though, and pretty rare at that....