when are tires too old to use again? i have a set of
 

michelin diaimaris tires that i put away with around 30k miles and was thinking of putting them back on after being put away for about 4 years. there are still inflated on these other rims but i want to install them on my current rims that i ride on now. is this safe to do?

why not have a tire shop inspect them when you are having them mounted

I don't see Y not, after couple of hundret miles just visualy inspect tires for anything unusual...:thumbup:

if they are down to the wear bars don't use them

Make sure pressure is adequate. That's all. Street tires are safe to use for at least 10 years.