"the main question is: do the tubes hold air when they are not on the rim?"
yes they do. ive pumped up all three and held em under water. no leaks
"if the tubes hold air, but always seems flat, maybe the valves are defective."
i was thinking that too but i doubt it.
"if your LBS can't figure this out, i don't have much faith in them"
im just gonna take this in on monday
no riding for me tomorrow